I need to reduce my bikes (2008 YZ450F) noise output by 4db's to be able to race Supermoto at a local track. I have a stock exhaust which was measured 89db at 16.404 feet. I also have a FMF 4.1 end pipe which measured 91db's. I have thought of either buying the FMF quiet insert with a muffler repack using extra packing or putting a stock WR450F pipe on it. A derestricted 06 WR450 with the pea shooter was able to meet the noise requirements if thats any indication to you of the required noise output. Any thoughts on which option to take? Edit: Forgot that the US works in imperial measurements, distance for testing amended.