Wild Bill from PSR told me that you will generally see a 20-30rwhp peak horsepower increase depending on what all you have done to your car. The more mods you have the more power they will make. But the best part is they make better power in the curve and extend the redline to 7000. Sweet2kstang is about to put this kit on my car along with a ported intake, his stage 1 ported heads, MAC LTs, MAC Prochamber, and Borla Stingers. Before the engine went down I was making 295 to the wheels. I'll be a little disappointed if I see anything lower than 345rwhp.