With stock drive ratios and a stock motor you'll see about 11 on a 89-93 blower and 12-14 on a 94-95 blower. 2-4 PSI can be expected from a 10% OD pulley. Porting heads, intake, installed headers, etc will all drop boost as there's less restriction to airflow. Installing pre-blower mods (cold air intake, TB, MAF Etc) will increase boost 1-3 PSI.
For instance, I run a severely altered and ported 95 M90 (the ones with the coated rotors). I have a Magnum Powers inlet plenum that had to be welded and ported to match the blower, a 75mm TB, a 76mm MAF and a MAC CAI all adding to the boost on the pre-inlet side. I also have moderate to highly modified heads, Magnum Powers front mount IC, a cam, headers and dual 2 1/2" exhaust which all work to lower boost. With a near stock drive ratio I make around 12-13 PSI. I can run up to a 23% OD by changing pulleys and make 17-18 PSI. However, I tend to break enough stuff with the stock ratio I haven't tried driving the car more than 10 miles with the high OD.
My point is, boost is relative to overall airflow restriction. Put my intake tract (everything from the air filter up to and including the blower) on a stock motor and it'll probably make 20+ PSI and blow it to pieces in about 10 minutes. Put all my after blower mods (IC, heads, etc etc) on a car with a stock intake tract and it'll stuggle to make 6-7 PSI. Mine barely made 9-10 PSI after ported stock valve heads and cat back exhaust upgrades.
For my first of many questions, what is the stock boost on a SC? I was hoping to boost 8lbs for safety, but i've heard 11.
