Not that it has to do with anything, why you running .76 commanded Lambda?

It you are at 90ish kpa, you obviously aren't boosted, why you running it that fat?

It should be about .87-.90 Lambda if you n/a, or you just hate your spark plugs and rings.

 

I did everything I could think of short of putting a gopro under the hood and doing a WOT pull, which I still may end up doing. Its the SLP lid, stock style paper filter (thats clean), stock MAF, tried both a smooth bellow and the stock crinkled bellow, stock throttle body and stock LS6 intake manifold. I don't know what could possibly be collapsing. Ive taken it all apart a few different times to inspect and can't see how any of that would be collapsing.

Mine was running 94-96KPA for WOT when everything was right, I have older logs of some WOT pulls and all was good.
Its overbuilt for the power it makes, its the stock block with a 383 forged crank and forged pistons/rods, 10.5:1 compression, PRC 2.5 LS6 heads, custom cam from patric G: (226/230 .598"/.609" 116LSA +3 advance)
Stainlessworks LT headers, their high flow cats and Y-pipe, corsa catback.
Stock LS6 intake manifold, throttle body, MAF, SLP lid with stock style paper filter.

I haven't done any WOT tuning myself, that was from the original dyno tune I got and I remember him saying he had to command extra fuel to get the wide band to read correctly for WOT. Mentioned my fuel pump might be getting weak and thats why. That was going to be my next question, could this be from a failing fuel pump? Fuel pump is stock and I made 433rwhp on a mustang dyno. I also have FAST 36# injectors that are supposed to be rated for more power than what Im making (unless the rating is for crank hp) and according to the scanner they are getting maxed out in the upper RPMs. If no one thinks it could be due to a fuel pump then Im going to remove the cats and look at them that way, as I said in an earlier post I had a endocope in the exhaust and could see them and they looked good.
Also the plugs that I have checked looked good, doesn't look rich or lean. Then again I didn't pull the plugs immediately after a WOT pull.
Also I pulled both valve covers off and checked for any cracked springs and everything looks good, still looks brand new.

 

Wanted to update this for anyone who has a similar issue. I edited the first post as well.
Problem is fixed, it was a corrupt tune file (or corrupt ECU). My friend tried an experiment with it on HPtuners and changed the OS(changed to 1 bar MAF (enhanced RTT) to see if it made a difference as everything else checked out fine and looked ok. Was going to try to replace the ECU with a used one but he didn't have any that would fit, so he tried this first, sure enough it worked and car is running normal again and strong. Super strange so I don't know if it was an issue with the hptuners software making a bad file or the USB link or the ECU but whatever it was its all working now.