172 gal, does the question relate to a measured lap time around a specific track/circuit or to straight line speed (if its the latter, Ill prob never know or care to find out). If were talking about a circuit lap, I can tell you that the same car lap times vary +/- 25% or more depending on driver. So given that everybodys 172s the same give or take a few bhp, the "fastest" 172 on the forum would be slower than the "slowest" 172 properly driven...Just trying to make a point that track time is the best performance modification for your money. Cars fine, its usually the driver that needs improvement. (on a scale of 1 to 10, Im still trying to get past 2 or 3 myself..)