General Maintenance & Repairs - Rough Sounds + Messed Up Idle

So I just had my fuel pump replaced by a dealer and now my car seems to have a few problems.

1. When putting the car into gear there is a rough sound from the rear of the car, hard to describe, it is kinda loud and sounds rough?

2. After putting about 600 miles on the car after having the fuel pump replaced I arrived back home with no troubles with the car (except #1). Went to Wal-mart and back no problems, then went out for some late night wendy's and it started it idle funny. Got to the stop light and it idle'd high for a minute then dropped down low to the point of almost stalling. Then at wendy's at the drive up window waiting for my food it cut in and out of high/low idle again but almost took off with my foot on the brake. Further down the road at a stop sign did it again then stalled. With a hard start I got back to my house still with the same problems. By high idle I mean around 13-1500 rpms, and low down to 3-400.

Any idea's? :confused:

Take it back to the dealer that did the work and tell to fix it. It wasnt doing that before was it?

Kinda sounds like a clogged cat. Any codes?

No codes, the thing I am really worried about it the idle/throttle. Once the car warms up and I come to a stop or even a cruise the throttle jumps and the car accelerates by its self. I am so confused.