I have a 1991 XR2. No major mods, open 2-1/2 exhaust, opened factory airbox, NGK's (1 step cooler), and a manual boost controller turned up to 11 pounds. I have an issue when the car warms up. When I go to accelerate from a constant speed or taking off, I get this tiny stumble and when I get about 5 pounds on the gauge (aftermarket), it feels like it has an engine brake engaging (or a choking effect) until you either accelerate more or let off and accelerate again. Another thing is it has a sound coming out of the exhaust that sounds like someone who is trying to play a trombone but doesn't know how to blow in the mouthpiece correctly. It doesn't happen all the time, but atleast once or twice on my drive to work.
Thanks for any and all help.