Do NOT let anyone talk you out of it IF you already have 200 HP. the ONLY reason I put that limit in there is because I don't own anything with less than 200HP so I can't be sure there is a difference. Like I said in my post before though, there WAS a noticeable difference with my truck. Even when flooring it at 45, I could tell the difference. Here's another one for you that people will argue with, Go get a NICE set of 8.5mm Pure Silicone plug wires. you will notice a difference. Check your cap and rotor (If you have one), if there is a decent amount of oxidation, replace them. You will notice a difference there too. The most important thing an engine needs to do to make HP is BREATH. Cold air is preferrable. If anyone disagree's with this, tell them to go take a physics course. Also, set your tire pressure correctly, you wont notice this in a straight line with the seat of your pants, but you can measure a performance gain in a corner and in a straigh line. I have a 92 Sonoma GT (Like a cross between a syclone and an S-10). I set the front to 40lbs, and the rear to 36. Trucks have a tendancy to understeer, so you want to have a larger tirepatch on the front than the back (If it didn't look funny, I would run wider tires on the front). The increased weight in the front does this for me even with the higher pressure. Most other front engined vehicles understeer as well (Unless they have a long wheelbase like a Viper).