I was just wondering if making small changes to things makes much difference to power on 250 cc bikes. Easy things like changing exhausts or air boxes. Nothing major just things that might make the motor run a bit more sweetly or crisply..if you know what I mean. My bike is a '91 Kawaski GPX 250R. Do they have restrictive mufflers on them? Maybe the standard exhaust has been fitted just to meet noise restrictions but could be a bit safer, as in cars can hear you easier, plus give a freer reving engine (plus sound better as well?). Is the air box restrictive? It is mounted under the seat with two venturi type ports in the lid. It seems a bad place for air as its right over a hot motor and the holes in the lid look quite small (Although it seems a good place to keep water from entering!) The venturi inlet size seems quite small and the air box volume is small. So was just wondering. Any ideas?