would a 2 1/2 in exhaust restrict too much exiting exhaust?.. maybe it would some how effect the air/fuel ratio? my thinking is we're trying to suck in more air then we can push out and maybe thats why we cant get good boost.. its not falling off down low in the rpm its up high(5,000rpm) where i think the exhaust just cant keep up with the amount of air coming in so we get little/no boost increase?

its just a thought cause at this point i'm running out of things that may be wrong...

we have a custom made 3 1/2 w/ a 5inch X pipe that will be going on this week, along with a cog belt system that will handle 16psi before it slips