Limp mode after muffler delete?

[ivancolesnic]

Cut out of the OE muffler (dual inlet/outlet 3? on 2500 HD) and replaced it with dual glass packs yesterday and ran like a scalded cat. Was doing a pull on the highway and hit ~100 at WOT in 3rd and 6000 RPM and bounced off the rev limiter (I guess, have it set to 6100) and now the truck feels poochy. Doesn?t pull as hard in 1st 2nd and 3rd at WOT, hits power enrichment just like it should (11.9-12.3 AFR), but feels like it?s pulling a heavy trailer. Did a log run to see if there was knock and everything was coming out clean.
Didn?t retune after muffler delete yet, but I can?t imagine that it threw my tables off that much that the ECU couldn?t compensate? Hasn?t thrown any codes. The only tuning I have done on the transmission is adjusting the shift points. No torque adjustments, etc. I have the 2006 Silverado SS shift table in it and the WOT MPH shift from third is set to 255 Mph so that?s what held it. Also my AEM gauge goes blank when I let out after a WOT pull until I tap the gas and then it comes right back to the 14s, could just be a malfunction? Or maybe something weird with the pulses due to the velocity at WOT and then me letting out?
Engine is a 6.0 with 706 heads, 10.5 compression and Truck Norris cam and bigger injectors.

[ivancolesnic]

I should also mention that it behaved similarly during my VE tuning a long time ago. Felt like the RPM ramp was slowed and the horsepower just wasn?t there. Now I?m wondering if I should be looking at my throttle body

[5FDP]

Could be a clogged cat if the truck feels slower than usual.

The wideband going lean after you let off is normal, it's called decel fuel cut off. It turns the injectors off and the engine turns into an engine brake of sorts.

[ivancolesnic]

I just had one out the yesterday when I was doing the exhaust, good thing I lubed up those slip joints, will be easy to pull apart. This does have the heavy duty and very large catalytic converters on it.
This problem seems to be intermittent and I suspect there is something wrong with my MAP or throttle body and the reason I say that is because the truck runs great in MAF only and is really finicky during VE tuning.

[ivancolesnic]

Oh also my return to idle in Park or Neutral is very slow - another reason I suspect the throttle body. This does have a 4L80e and the HD torque converter

[Alvin]

You'll need to scan it and find out what code it's tripping while in limp mode.

[ivancolesnic]

Drove the truck again and it has two codes pending for knock sensors. P0332 and P0327 low voltage. Power is good until codes pop up. It has new sensors (Dorman) torqued to spec and new pigtail. I looked at the timing retard table and it looks like its pulling timing (5 degrees) around 3k RPM. I?ve heard of people getting false knock from longtubes, could my dual 3 inch with glass packs be causing the same issue? I am running the stock 2006 Vortec SS timing table on 93 octane, so I don?t think it?s actual knock.

[SiriusC1024]

False knock wouldn't trigger the codes. Pulled timing is due to the fault detected.

[ivancolesnic]

So does the low voltage mean knock or issue with the sensors??

[SiriusC1024]

Sensors or wiring.

[ivancolesnic]

Ordered new Delphi sensors, have a few wiring harnesses to try too.