Engine swap 5.3L to 6.0L Tuning Advise

I had a shop replace the 5.3 with 215K miles, in my 07' Avalanche 4x4 LT, with a rebuilt 03' 6.0L, LQ4. (The 6.0 block casting#12551364), rebuilt 317 heads. All new ARP hardware and gaskets, new oil pump and water pump.
They re-used the 5.3 exhaust manifolds. Stock 6.0 cam and lifters. An upgraded newer style 100mm throttle Body, stock MAF, new ACDelco 36lbs. injectors, new ACDelco Iridium plugs and new wires. Two new Denso upstream O2 sensors. Reused the 5.3 coils. The original 5.3 was FLEX Fuel and had the active fuel management. The 6.0 does not.
Nothing was done with re-programming the ECM. My question is; should there have been re-programming to the ECM for the larger displacement? Currently I am using the truck as a daily driver. I would like to get the best mileage and performance from the up-grade, if re-tuning would be a benefit.

07 Avalanche 5.3L would be a Gen 4 58x reluctor engine and a 03 6.0L LQ4 is a Gen 3 24x reluctor engine. What did you do about that?

How the heck does it even run right with a 100mm throttle body too, that's way larger than stock.

This is the reason for the post. I personally did not do anything, a shop did. This is why I am asking for input on what was done. The truck seems/feels to run exactly as the original 5.3 did...

Again, this is why I'm asking. What can or should I do different with what was done? Does something that was done need to changed? If changes are made, what would they give me?

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Originally Posted by Cyborkop

Again, this is why I'm asking. What can or should I do different with what was done? Does something that was done need to changed? If changes are made, what would they give me?

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The tune will need to be changed in order for the 6.0L to function to its potential.

If you don't understand the differences in a Gen 3 and Gen 4 engine and don't know what would have to be done to a Gen 3 engine to make it work correctly with a Gen 4 ECM don't even attempt tuning.

Correction to my original post. The throttle body is stock 87mm. I will not be doing anything myself. I will hire an expert to do the tuning. I'm asking so I don't waste money if not needed.
I'm trying to get it done correctly and hopefully see overall improvement. Is there something that stands out in this build that should be addressed above all?
Like should the ECU be changed out to a GEN3?

This doesn't pass the smell test......
You should take it to a reputable local tuner with the phone number of the shop that installed the motor. Don't do anything yourself from this point forward. Don't give any info to the new tuner other than the phone number and name of the engine installer

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Originally Posted by 2xLS1

07 Avalanche 5.3L would be a Gen 4 58x reluctor engine and a 03 6.0L LQ4 is a Gen 3 24x reluctor engine. What did you do about that?

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While GM started putting Gen 4 LSx motors in 2005 models, they were still using Gen 3's into early 2007. I don't know when they transitioned the Avalanche, but very well could have been a Gen 3 in it to start with.

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Originally Posted by Paulster2

While GM started putting Gen 4 LSx motors in 2005 models, they were still using Gen 3's into early 2007. I don't know when they transitioned the Avalanche, but very well could have been a Gen 3 in it to start with.

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He said in the OP that the 5.3L had AFM. That makes it a Gen 4. And I have never seen an 07 Avalanche that wasn't Gen 4. There was never a 07 Classic Avalanche.

The original person and shop are no longer around. Because of that I started my own research based on what I was told up front. In my research I found I was taken advantage of and then some. Not a lot of what I was told and had in writing turned out to be true. Again, this is why I am here now gathering as much info as I can before I put any more money in the engine or tune. Going to an HP Tuner later this week for him to look at the engine with his laptop...
I thought I'd get suggestions on what to do going forward if anything. Saying the tune will need to be changed still leaves me hanging... It sounds like it's open to interpretation of the tuner. I would not think this is the first time this ever happened.

The 5.3L was a GEN4 originally.

Even in a circumstance where everything is known, tuning isn’t really something that can be explained as change this and this and you are good. It’s an extended learning experience requiring reading everything on here that you can, reading some of the books on the subject and watching a lot of YouTube to get you started.

Add in that you may have a real mixture of unknown parts (MAF, MAP and injectors as just a start) plus who knows what other problems and it gets that much more complicated.

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Originally Posted by 2xLS1

He said in the OP that the 5.3L had AFM. That makes it a Gen 4. And I have never seen an 07 Avalanche that wasn't Gen 4. There was never a 07 Classic Avalanche.

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Fair enough.

I think I understand much better now, after your input, thanks. Since I need a tune and the GEN4 ECU is locked, money wise and tune wise, would it be better to invest in a GEN3 ECU that is already unlocked? Would everything on the truck work with the GEN3 ECU, like the transmission?

If it’s locked it’s been tuned. Maybe not for your setup but it’s been tuned.

Don’t think the gen3 ECM will communicate with all of the other modules in a modern vehicle.

This doesn't pass the smell test......

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Originally Posted by Cyborkop

I think I understand much better now, after your input, thanks. Since I need a tune and the GEN4 ECU is locked, money wise and tune wise, would it be better to invest in a GEN3 ECU that is already unlocked? Would everything on the truck work with the GEN3 ECU, like the transmission?

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Do you understand the difference between a locked/unlocked ECM and a licensed/unlicensed ECM? And no you can't use a Gen 3 PCM in a Gen 4 truck. Do you even own HP Tuners?

I understand the difference. The truck was read by a professional HP Tuner a month ago. The reason I am asking all the questions is because of what he saw done incorrectly by the original builder. The factory ECM was never touched by the original builder after he put in the 6.0. It's currently bone stock as it came with the 5.3. Anyone tuning it would have to pay credits to unlock it to program it. Based on the recent replies to my question I'll have the GEN 4 ECM unlocked and programmed for the 6.0 upgrade with the larger 36lbs. injectors. It may not be much of a tune, but hopefully it will provide some improvement. Thank you everyone who provided positive feedback.

If it is any help. I went through basically the same operation as you. Except my Silverado was an 09 and I removed the 5.3 and installed a 6.2. I had to put bigger 52lb fuel injectors because I still have an Edelebrock E-force supercharger to put on my 6.2. But yes for 6 months being a green tuner I have been tuning my 6.2 and it runs awesome. Much more power than the 5.3 with AFM. Once you get your license I might be able to help out on a program for your truck. I put a mild cam in mine with headers, and getting the balls up to install this supercharger. I don't know how much more torque it can get than what I have now. But once you get it tuned you will love it. Good luck