Tim,
Depends on what you're looking for in a pylon racer. If pure speed is what your after, some thing Nelson powered is what you want (the die-hard racing guys can set you up on this in the pylon racing forum). For us mere mortals, my club back in St. Louis (
http://www.spiritsofstl.com/) races with other clubs using the stock Sig 4* (kit or ARF) powered with box stock Super Tiger GS-40's. Racing is run a a 2-pole course, 660 ft. spread. Fast time limit is 2 minutes. Fly faster and you'll be disqualified.
An old, but great pylon racer that is dynamite sport plane is the Scat Cat 500 is still available through Lone Star Balsa (
http://www.lonestar-models.com/) for $49.95 + S&H. I have one that was used for a bit of racing, but mainly for sport flying. Built around 1981 or so, it has over 2500 flights. I've also had the Andrews Quick Ray (of Lou Andrews fame) and, the Bridi and Spickler planes. All where quite fast, but I think the best over all has by far been the Scat Cat. Very rugged - just glass the center section to within 1" of the ailerons and the wing almost indestructible.
Hogflyer