my puch normally maxes out at a little over 25 mph. I had a STOCK tomos pipe sitting in my garage so i rigged it up to fit on the puch (the pipe comes out the other side of the bike, so i attached it to the kickstand with some wire!) the result was that the acceleration stayed the same, if not better. The top speed was somewhere between 30-35 mph, according to the speedo. I dont know what the biturbo will do to a puch in terms of performance, but a stock tomos pipe is much cheaper than a biturbo. (i have seen stock pipes go for $9 on ebay!) just a thought for some puch owners out there