Can you speculate why the B&B's put down so much more HP and TQ?
I can. Something happen during the header swap that caused the PCM to behave differently on the second runs. Perhaps depowering the PCM erased codes, or perhaps a sensor was re-plugged in or code got erased.
I made it a point NOT to unplug the battery or do anything else that would change ANYTHING else on the car. I had to know if this was why this car was low on power. I even plugged up the DRB and noted all adaptive memory cell numbers as well as all other operational parameters before the install and verified that nothing changed after the install. I did the dyno runs at the same temperature reading on the DRB. The B&B run was run #3 and the car was actually a little warmer than the Belanger run (#1). I forgot to hook up the RPM lead on run #2. The car actually has a fault in it for the oxygen sensor, it is still there. I will put new oxygen sensors in it tonight.
As far as speculation, my opinion is that this engine, which is 510 CID, could not exhale well enough through the headers. The boost pressure actually dropped 1/2 pound after the install. In addition, I also built this exact combination on another car that makes 738 HP, with TNT headers, the only difference in the two cars. I even put that VEC program in this car when it had the Belanger's and it STILL wouldn't make any more than 650 HP. My speculation is the Belanger's don't flow well enough for a large cubic inch, forced induction car.
DW