If you want true performance, I'd invest in a new ECU. JWT makes a good one for the Z31. I've never seen anything but problems with chip mods. Up to and including complete ECU failure.
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1992 Yamaha FZR 1000. 145 Hp, all stock..
I dunno about a supercharger, but the N/A engine could be turboed with a little work. Its been discussed before in the Z31 section. Try searching in there.
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1992 Yamaha FZR 1000. 145 Hp, all stock..