I love white bikes. my old one was reflective white, I have it broke down and I am going to use the white as a base for a faux marble finish. White is sooo hard to keep clean looking with all the road grime that accumulates.
About the white paint. I didn't have any problems with painted exhaust until I switched to the expansion chamber. Dupli-Color ceramic engine paint works well on the standard exhaust. I have used the black and I had no peeling. The Expansion chamber is a different story though. The paint peeled around the bend at the intake, so it must get relly hot. Whenever I get my other bike finished and swap parts from current bike over to older bike I can repaint and I think I will try exhaust enamel, because it is rated up to 1000 degrees. Another possibility is that you possibly didn't cure the paint properly. I have had issues with enamel curing... its so freakin' time consuming. next time I paint my bike I will definitely use lacquer with enamel clearcoat.