I have used the STP fuel system cleaner and castrol fuel system cleaner and now I just tried the VP racing fuels Fuel System cleaner and I can really feel a difference.. seems to idle smoother and acceleration seems to have more response as well. When I used the STP and Castrol, I felt no difference at all. Of course it took maybe 100 miles of driving around for me to start feeling the difference in the VP. I dont think its just me cause I pretty much live in the car lol. Any feedback on the VP FSC? ANyone else tried it? I was going to try the Synpower FSC sometime but after using the VP, I dont want to try anything else.