Nothing wrong with banshees, they run great. Go over it give it a compression test, make sure it goes through it's gears fine. They are really easy to work on, there's a ton of cheap aftermarket parts around, there's nothing wrong with aftermarket reeds not really going to see much Hp gains with...
When I rode the xm felt the same way, felt a little doggy like you said. I have a 11 etec with rooster built clutching feels a lot more responsive, on and off the throttle it hits 8000 a lot quicker , I snow checked a 14 etec and rooster clutching will be the first thing I do to it.
I was out riding the and my sled seemed to have a slight sputter at full throttle, then i would come off the throttle and get back on it and it would bog? Any ideas? Could it be the reeds again?