Is that with or without vacuum going to the regulator? Boost could be limited by a vacuum leak, map sensor or bad actuator.

Stage 3 is a lot of fun...

That's good to know... the Corrado came here in either G60 supercharged version or later on VR6, so it's probably Jetta/Passat, although the Jetta lost the 2.0 16v option after '92.