It's not really just about boost pressure - it's about volume of air that needs to be moved. Obviously at higher pressure there is more volume, yes, but it's not always needed. If you're going to be running an intercooler get one...hell you should just get one anyway they are nice.
well, above 12 PSI you NEED an intercooler.
If not you are actually stealing more power than your trying to make.
Unfortunatly, when you put an intercooler on, you need a bigger bypass valve (assuming it flows decently) or else you will get compressor surge so bad the car will not drive. The stock one can not flow enough air. Hell, 3 stock ones cant, i tried it. I have the mini race valve and love it. Worth every bit of the $175.
The paxton unit is ok, small, but ok. You still need that valve.
only issue i ahve, is that the inlet in the power pipe is the stock size. i need to find the correct size aluminum bung, and my friend is going to weld it up for me, and close off the stock port on the bottom.
Well on mine with an IC and 10psi with stock BPV the car was going crazy. I drove it home from Fort Wayne because I was going to have the aluminum bracket for the mini race welded on by some place else. Anything above 50mph the car would buck REAL bad when Id let off the gas.
When I got home I had hole where the BPV went drilled bigger but I never thought about the one on the Boost Pipe. I drove it like that untill I put the new engine in and then I fixed the hole for the boost pipe when everything was appart.
One problem I had when the boost pipe hole was not 1.5, the pipe on my IC would always blow off. Since I fixed it the proble went away.