I just ordered the Ti Powercore (muffler and midpipe, im gonna stick with the stock header) for my '05 WR 450, and I have heard both sides, that I do or do not need to re-jet. I have made some jetting changes after I did some of the mods (throttle screw, baffle, remove AIS, "gray wire mod", fuel screw), and the bike ran great. I imagine I will need to rejet, and I was hoping that I can do the installation of my new pipe and rejet it all in one fail swoop. I ride at 4000 to 6000 elevation, and right now, the temp. is 40's to 60's. I REALLY appreciate any help, I cant wait to get this baby dialed in a go tear it up. Thanks in advance.