The frame sliders you found on ebay are for the bolt father back, that goes all the way through. IMO that's the best place to mount sliders, as it's less likely to damage the cylinder head (pull the threads out) in a crash.
Most non-cruiser motorcycles use a separate throttle body per cylinder. Balancing them is adjusting them so they're the same amount open at idle. You check balance with a vacuum gauge, vacuum for the two cylinders should be the same.
The TPS or Throttle Position Sensor helps the ECU know when you're opening the throttle, which helps it operate smoother when you first start opening it.