I have an 88 turbo with just a few basic mods including a large intercooler with 2.5 piping and 3 inch exhaust. Nothing else majorly different. But at WOT It builds 10psi then as rpms increase the boost decreases until it settles at ~7psi. Could it be possible that I've already maxed the turbo out? I wouldn't think so but nothing else makes sense. There are no leaks and the car runs great. What do our ct26 turbo max at?