I just bought a '99 wr400. The guy changed over to the YZ cam timing, put an FMF header on it, and supposedly had it jetted at his local shop for this setup. At idle, the header turns faintly red hot. Also, I get a major hesitation if I gun it at low rpm. This tells me it's jetted too lean - but I'm new to the bike and could be wrong. BTW, it runs great above idle and starts easy. Can anyone provide a pointer or two? I don't want to ride it with a red hot header. Thanks.