I haven't hade any problems with my GO 0801 pipe. On the 5 port this pipe is crazy, I run this setup myself. For some reason my motor never gets above 200 degrees and has all the power I need. To boot that I'm getting 11 minutes on it in my Matrix TR with the stock carb resrictor I pitted twice in the 30 minute main, this past weekend at the LA points series race

5 port + 0801 = Killer Combination