Just ordered the Thunder Alley pipe with ceramic coating and spark arrestor for the WR450. Should have it 4 weeks. Bob Murray at Thunder Alley says his pipe works well with YZ or WR cam timing. The guys over on the YZ forum swear by them. Seems to be designed for a huge bottom end to mid rev range power increase with no gains up top. Has anyone on this forum got a Thunder Alley pipe on their WR450/426/400? Feedback please.