2016 sierra 5.3 Help with long tube headers no cats.

[GHuggins]

Your tune file I was going to check and see if I had the definition to just make the change quickly for you in regards to the etc max and effective area tables.

[bk2life]

But since you likely cannot, you can do a few things to make it not pull so much timing. The reason its pulling so much timing is that your throttle and torque values are incorrect and its going crazy. An easy way to keep it from doing that is to raise the minimum spark split injection table. This will keep it from dropping to very low timing values on start, but the startup idle rpm may race a bit. Then you need to adjust the base and split airflow tables to get this back in line some. Then there will be virtual torque and VVE changes to get it in order. Essentially, you have the tables to solve your issue the HARD way. HPTuners no longer allows for Cat Warmup to be turned off and also doesn't expose a dozen other tables that could be helpful. I know tuners who have sent HPTuners definitions for things but HPTuners still doesn't add them. They have no real competitor so they aren't going to ever answer the questions or comments. User Defined parameters was there way of appeasing the needs...but 99% of tuners don't have the ability to decompile code and find hidden tables.

Anyhow, yeah you have quite a few things to work on to get it to play nice on startup. Removing the rear O2's is another issue on E92 ECU's unless you have access to background tables to turn off the fuel checks. Otherwise the car will forever run a fuel test every so often (typically 2-3 run conditions immediately after filling up with fuel) to verify the rear O2's are responding properly. With the O2's missing, the ECU see's no response and ends up pulling a lot of timing and dumping in a lot of fuel to get a response. I've seen the timing go into the negatives and Lambda go into power enrichment levels at idle due to this. Fortunately I think there is a timeout limit where the ECU will stop trying to run this test and get no response and since you have the O2 codes removed, it wont set a CEL. But then when you refill the fuel tank it seems to reset this timeout and try all over again for a set number of test attempts. This behavior was observed by myself and then with some background tables it was solved and these tests no longer run. But again, HPTuners doesn't expose the tables needed to solve this in all E92 vehicles. I have seen some vehicles that have the table defined by HPT though and its only in the latest Beta..

all of this is pretty well mirrored in a thread io made nearly identical to yours about a month or so ago.
I have a 2014, and have done the bigger intake and throttle body. I think i only cnaged the intake voulme and scaler for the throttle body size. Nothing else was changed at that time and i have no issues with the tune for the intake/tbody. - yes it made a difference you can feel in the upper rpms.

I just recived rear o2s yesterday, and will be installing them hopefully this weekend. Again, my truck and your truck sounds very similar. You can search my name and find my other thread that is nearly identical to this one here