After I added the long tubes and had the GTO tuned I was suprised at the small (~10HP) gain. The HP stopped climbing with RPM relatively low, so we suspected that the belt might be slipping, letting the boost level drop at higher RPM.
A friend of mine helped by video taping after I added a boost gauge to see what was happening.
The video lost some resolution uploading to Youtube, but what I saw was a bit of a suprise. Rather than dropping, at about 5,000 RPM the boost level starts creeping from the normal 5 PSI up to 9 PSI at redline!
I've got some sort of restriction that is not capable fo flowing enough air through the engine at that RPM, so the air is backing up in my intake manifold!
Hopefully my new cam with a LOT more lift, and a LOT more duration will help.
I also want to keep an eye on fuel pressure. It does drop a bit near the top of the band, but it is still within spec, and my tuner said the A/F ratio was holding steady all the way up to redline, so I am OK there for now...
Another thing that might be hard to see is the speedometer. I hit the gas at 20MPH, and just a few seconds later I let off at redline doing over 70 MPH in 2nd gear!