easy. it's either 2 simple things:

1. needs a new IC pump. the stock one always fails. get a johnson CM30, you will get your power back. when the pump fails, the heat-soak stops the supercharger from engaging.

2. you may be experiencing the throttle-lag. get a sprint booster for this. our throttle is electronically controlled, so there is a delay when you mash the pedal, the sprint booster speeds this up!

low end torque is AWESOME once you replace either of these! trust me! VERY seriously doubt this is from belt slippage at only 20k miles. and i haven't heard of that on here. it's almost ALWAYS the IC pump or throttle-lag.

also, look under the car and look for any tranny fluid leakage, this is another thing that always has to be fixed(once only)

the burnt smell..... could be a bad catalytic converter. i have seen this come up a few times with others on here.