Quadzilla 500 it has" fmf" gold series and I am looking for a better pipe.

The FMF Fatty and Bills pipe hits at a low RPM but will not Rev even with radical porting.  The older FMF gold series runs similar to the Paul Turner pipe as far as the shape of the power curve. 

The new generation of "large Belly Pipes"  Aaen, DCS, Q v1 and Qv2, HPR-19 make more mid-range and peak power while some will rev higher than others at the expense of loosing low-end.


Most of the older small belly diameter pipes often excel in only one RPM range while others are duds in my opinion at all RPMs.  The new generation pipes tend to make more power over a wider RPM range especially when matched up with the rest of the engine components.