'98 Regal GS mods
I finally had the S/C pulley changed (from 3.8" to 3.5") last week. The max boost increased by 3 psi (7 to 10). My mechanic said 3 psi translates to about 24 hp (1 psi of boost = ~8 hp). He also installed an IAT module that tricks the PCM into thinking incoming air is colder than it is. He said it should give me ~7-8 more hp, which is what SLP claims. With my new K&N air filter, 3.5" pulley, and IAT module he thinks it should dyno at ~275-280 hp, and ~315-320 ft-lbs of torque. He also said to make sure to only use premium gas. I CAN feel a big difference at launch.