Lack of fuel or too much timing causing detonation and then the resulting timing retard would be my first thought.

 

I agree with James. Also when I had a nelson tune and checked the tune with tunercat(now JET DST) I found that I still had some torque management left on. It made a big difference for me getting rid of all of the TM with tunercat.

 

I still havent seen what method of fuel delivery you have for you setup, I would if you havent already swap on a GMPP RAM -JET manifold . Got a friend in michigan who did this mod to a L31 silverado / with a custom front mount turbo and its bad! James B. is right, the stock manfold is a limiting factor.

 

How do you get 550rwtq with only 6psi on a Gen I Vortec engine? I also doubt there's 252* of timing, the engine just physically wouldn't run. It might be commanding that but that's not what happening.

 

Not too difficult actually. Stock torque is 330ft.lbs at only 2800RPM. Move the power up in the range, open up the exhaust, cam it, fuel it, boost it, tune it and 6 psi will put you right there.

 

330 at the wheels stock? I don't think so. 550 at the wheels with a $1000 home made butt turbo, stock fueling and manifold. Hell, we don't even know if he has a cam in it yet. You might be talking at the crank, but I'm talking at the wheels, because the likely hood that he engine dyno'd a rear mount turbo system is small.

We need more info on the setup!

 

I got a reading of 580 ft lbs of torque on the transmission section of my snap on scanner. I really dont feel that the truck is powerful enough to be putting out those numbers but thats what the scanner is telling me. right now its a stock fuel system. I have a 355 lph coming now . I put in a meth injection system. The cats are still in it and a flowmaster muffler for the exhaust. once i can get this problem straightened out im going to put in on the dyno. I also have a wideband o2 sensor coming and exhaust wrap