The stock '99 pipe is excellent for trail work. There is no need to change the pipe on the '99, IMO. Spend your money on suspension or a steering damper instead.
I bought my '99 from an AA enduro racer/A cross country rider, and he told me the stock pipe worked best. My bike is like a magazine project bike as far as aftermarket parts, but it has a stock pipe. I love my bike offroad, epsecially the Factory Connection suspension.
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