[suicideneil]

I ran those number through the calculator, and it says you should be doing about 32mph, which does seem a bit slow for that setup I must admit, so it may well be undergeared. If the motor is hotter than the esc by a long way, then I would suggest going down on the spur and up on the pinion (spurs are cheaper, but there is a limit to how small you can go/find with 32p gears). As for the KB45, I dont know what kind of amp draw they are rated at, so you would need to try and track down some specs or find someone already using them- there are a few on RCM so its just a case of doing a little looking around really. The L can sized version would be similar to the XL feigao I reckon, but the XL sized version should be a good bit stronger in theory, given the same length but a larger diameter & larger magnet.

Batteries however is another thing entirely. If the old maxamps packs really seem to sag under a heavy load, or heat up more than is ideal, then it might be time to upgrade to something higher spec for the more powerful system, and save the old batts for smaller vehicles. I'd look and see what other people run for the best idea, but anything with over 5000mah and 20c is a good bench mark I believe....