So I have an '06 XR650R with about 200 corked up kilometers on it. I decided to uncork this thing and did the usual drill: airbox snorkel/plastic thing out 175 main 68s needle in the third or middle position UNI air filter Comp spark arrestor drilled intake manifold I am by no means skilled at mechanical stuff, but this was pretty easy. This thing sounds like a beast now. Can't ride it yet cause the temperature dropped to about -10 Celsius so its too damn cold. So it is killing me to see the performance difference. I have two questions - With all the above mods I did, how would it run if I left the stock spark arrestor in the muffler instead of using the comp spark arrestor? Only reason I ask is that it is a tad noisy for 0430 hrs drives to work..... Secondly, I couldn't get that stock metal screen to fit behind my UNI air filter.... will that be a problem? Thanks for the help... if it wasn't for this site I wouldn't have been able to uncork this beast myself.