First, forgive my noobishness, still learning about all this, corrections welcome. I'm thinking about getting an aftermarket exhaust for the vtr250, mainly for the sound. However talking to someone today, mentioned watch out for drop in compression (back pressure?) Also - I read that without rejetting (or shimming) carbs the mixture's too lean and you get a flat spot in the torque curve round 4,000rpm. Both of these seem to make sense, to me. If you get the exhaust and rejet would all be good? Or is the exhaust one of those things that is engineered just fine and should be left as-is?