Another idea to think about is adding in a reed valve kit, that'll give you better bottom end performance with less top end loss. The advantage of the reed valve is there's no blowback at lower rpm's and once the charge enters the case it can't back out into the intake manifold or thru the carb so there's also a fuel efficiency gain that comes with it. The kits they sell at JNmotors and a few other sites will do just what you want since you're not looking for top speed, there are bigger and better reeds available for the screamer engines, but the RSE reed kit does really well for smoothing out a rather stock engine... http://www.jnmotorsbikes.com/product_p/jnm1252.htm
These also work really well when there's no room for a longer intake and for a nice clean looking install with the carb in almost the stock location.
These will lose a little power on top but not as much as other mods can.
If you need to keep the price down tho, adding length to the intake and exhaust pipe can get you similar results, you can actually tune your engine to make the best power at a certain rpm by changing the length of the exhaust pipe or intake manifold, or both.