A belt will not give you any more power. It will only increase the HP going to your wheels. You will not get as much slippage with the new belt either. Your best pipes should have a clutch kit that is manufactured for that pipe to get the best performance. White brothers is good but there are other companies that have whole kits that will give you better power than just a pipe. 4 strokes are harder and much more expensive to mod but they can be made to be really fast. LONG LIVE 2 STROKES!!! Sorry I had to put that in there. Now that you have the pipe call and see if they can set you up with a clutch kit for that pipe.

 

My Scrammy dynos @ 47.5hp on the dyno. I had a clutch kit installed at my local dealer and thought it was the worst thing ever. I am now using the stock set-up again and have no belt slip. I can outrun mildly tuned z400 and 400ex quads by one and two bike lengths respectively. I can wheelie on demand, and blast trails like no other. Clutch kits are awesome for 2 stroke quads. They have a powerband in the upper rpm and use clutch kits that come in higher. Because they have no bottom end. Four strokes are all bottom end, and if you go with a higher clutch engagement you are defeating the whole purpose. The E-series pipe is awesome. When you buy a jet kit you get full instructions on how to install it. The kit includes the better fuel needle and main jet. You will notice quicker throttle response and it will bring your pipe and filter all together. It is not hard to put in, but is a little time consuming considering all the stuff you have to move to get to the carb. Your local dealer can put it in for a good price if you would feel more comfortable. Total cost for dealer installed jet kit should be around $100-$120 at the most. If you want to modify your quad this is a necessary baby step.