I have an 08 WR. Rode it only briefly when new with all the free mods, the AIS removal kit/jetting and opened up stock muffler. Power was good but not great. Went to an FMF Q4 and it totally woke up the power. Then added the power bomb header but didn't perceive any additional change. Recently crunched that header and went back to the stock until I could replace. This time I did notice that the power got a little softer, little less hit. Probably more sensitive to it cuz I've got a lot of saddle time on the bike now. I just received a YZ header purchased on ebay to install as Im not convinced that the power bomb is worth the extra cost over just a larger diameter standard YZ Guess I'll find out on the next ride. BTW its a Chinese stainless steel OEM knockoff that include the brackets for the stock heat shield. Very nice fit and finish.