RE: fg big power pipe ?
Not much power gain at all. I raced FGs years ago and I did use the big power pipe. In racing it is nice because in a hard side hit the pipe does not get damaged. If you are looking for more speed I would pass on it. In fact I think it might cost a little power. Also, the center of gravity is changed to the downside. Much more body roll with the big power pipe. I did use them and did like it due to less DNF chances. I also removed the packing in the rear portion of the pipe. It would not pass a decibel meter test through IFMAR with the packing removed though ( makes it quite a bit louder). If you do go with it buy an extra plastic sleeve that is used from the header to the pipe and use the extra sleeve to fasten the back portion to the main pipe with hose clamps. The size is off a bit so just run the motor to warm up the sleeve and slowly tighten the clamps down to make the larger plastic sleeve fit the smaller front portion of the pipe. The O rings on a stock big power pipe will not hold it together for long w/o the help of the sleeve. Good luck!