I have an 03 636 and my pipe is pretty broken. The tip is missing because (I'm pretty sure) the guy I bought it from tried to make it into a shortie and failed and lost the part he cut off. Anyways, I have no back pressure and I'm wondering, would that affect the power so much that I couldn't do a power wheelie? I plan on getting a new slip on in like two weeks anyhow but I was just curious. Thanks!