88-92 powervalved engines are superior on the track. the powervalve is the same size as a lt500 aswell as the reeds.

 a plus 2mm piston will slightly increase case compression.  as would moving the reed closer to the piston.....
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i like the dyno that ice racer posted.  there clearly is no " best exhaust" »» THEY ALL MAKE THE SAME TORQUE» the paul turner is great for 6000 rpm. the dyno port is great for 7000 rpm. the ftz is great for 8000 rpm.  everything else is just ok.....