I have a white brothers R4 without the air lid, and getted correctly, also i flipped the rear swingarm linkage around to lower the back end a few inches. that right there makes the raptor power mroe manageable. but the R4 pipe i have on it i love, white brothers have been around for a long time, and they are only 4 stroke mufflers. I belive that they know what they are doing. but that pipe really opened up my raptor a ton. but that is just my 2 cents.