As everyone knows I have the HRC stageII with NO leaks. I did the cover turbo (where intake goes) and it died on me. The problem I am having is when I boost at 6psi without boost controller it falls back to 5psi at higher RPM'S. When I use boost controller at 9psi it falls back to 8psi at higher RPM'S. What, other than intercooler/turbo leak could cause this? Its pissing me off.

Exhaust leaks.

Start your car and let it idle while you cover the tailpipe with something. The backpressure will increase and you'll hear any leaks you have. it helps to have a friend at the front while you cover the back..

The exhaust leaks would have to be before the turbo though. Like in the manifold. But wouldnt you hear a leaking manifold? When my turbo was installed I had to torque down the manifold better because there was a leak in the gasket and it was really loud.