Neon

Hi I have a 2001 Plymouth Neon with 66,000 miles and it is a 2.0 liter engine. For a while now my exhaust is making loud noises when I stop at red lights. If I shift the car to Park, the noises stop. So basically only when its on drive and on a red light. Also it only makes the noise when the engine is fully warmed up. It doesnt make the noise until engine collent temp is at 50 percent. Also about 10 percent of the time, the car jumps a little when I push on the gas pedal after standing on red. If I floor the pedal, it does not do the jumping. I dont know whats the problem, maybe you guys can help thank you.