Everytime I let off on the throttle...
 

and the car humps forward i hear a thump. Is that a bushing somewhere going bad?

I got the same thign man, Ive been told its either the PPF (Power Plant Frame) or all the bushings. I want to start a Group Buy soon for Jim Labs Unobtanium Bushing Set. Stay Tuned ;)

I havn't had a problem with this until driving long distance today in WARM weather. It's been pretty cold lately but now that its warm, everything is moving easy, especially things that make annoying sounds. Hard to push out these bushings?

You need like a something ton press. Its not hard if you got the press. Best bet is take them out, and take them to your local mechanic for him to push them out.