I just bought a '99 WR4 and the stock exhaust insert was already removed and lost. I want to quiet the bike down and it looks like the WB Vortip is a good way to go. Unfortunately the WB catalog only lists a Vortip for the '98 and '00 WR4s. Does anybody know why the Vortip wouldn't work on the '99 WR4? Does the '99 exhaust have a built in spark arrestor? Thanks.