Mc28 actually does have a stock exhaust restriction - washers in the pipes. If you unbolt the exhaust, you will see them. I spent about three hours per pipe grinding them out over the winter.

Not sure what the actual power gains are, but the bike does have better pep now, and pulls to about 12.5k. Before it felt like it hit a wall at 10k.
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1996 NSR250 SE
1997 CBR900rr
1989 Hawk GT
2000 996