You have a problem here. If you truly have a trail port, going to a mid-top exhaust is going to narrow your power window and take away bottom end, and then start robbing the lower part of the midrange. You have way too big of a carburetor for a trail port and for running pro circuits. You should be down around 28-30mm's (pro circuits peak at 8,800 rpm). I would imagine right now your missing out on a bunch of bottom end with such a big carb, and the throttle is probably not as crisp as it could be. To do this right, you need to have the cylinders re-ported so you can use the full potential of a mid-top pipe.