the boost varies between cars. mine is 6 pounds stock. some are 5.5 and others are 6.5. but in short, its about 6 pounds. even with all the supporting mods, running 15 psi is over the limit and you will eventually blow the engine up (rods are too skinny). alot of ppl are happy with 10 pounds with fmic, full exhaust, engine management, and a couple other bolt ons. even at 10 psi, you are risking the life of your engine. the msp engine is identical to a stock protege with a turbo slapped on. if you look around, there are quite a few threads that will warn you about what happens when the boost is too high. im gonna tune mine at 11 psi. i just picked up a long block from a junkyard so that when my engine goes, i will have a rebuilt one ready to go.