JoeNova

You have a .56x lift cam with a .650 lift spring. Chances are, around .560 lift, your valve springs are buttery soft and don't have much pressure. In comes the valve float.

V-10 Killer

iTrader: (22)

That does really look like what I'd expect for a boost controller Overboost Shutdown. It'd be interesting to see a run showing manifold kPa. Could always be something else, but...

ZNix

iTrader: (1)

Two things I am seeing... One, stop with timing. I am a big fan of low timing and more boost. But that's just me. I run a maximum of 18* on methanol and 93. Over 30lbs of boost though. I think this could be valve float myself. The springs are pretty good on the seat, but opening pressure is going to be low I am sure. If I calculated the pressures right, you are seeing just under 400lbs under total lift. I'm not very familiar with LS engines, but I would probably want to see mid 400s no? I would also like to see a log of manifold pressure if possible.

93camaro_zzz

iTrader: (13)

I am willing to bet that it is sucking the inlet tubes closed. APS kits had a big problem with this. I had an APS kit on my car back in the day, and I quickly replaced the intake hoses with metal versions. Next, I would be looking at valve springs.

93camaro_zzz

iTrader: (13)

Also, I just re-read your post, and I agree, it is dynoing very low. To put it in comparison, mine did the following back in the day.

370ci, 8.4:1
AFR 225s
Proflo-XT
T-56
9psi
607whp

Shortly after that, it ate the turbos. Story of an APS owner's life.