Strange suspension noise / AC vs. Idle

[DAVPX]

I thought it was just because it was cold in the morning or maybe just new car bugs but I hear a creaking/grinding sound coming from the rear of my V whenever I go over speed bumps or even just when the road isn't perfectly level. It's a rather faint noise but surely noticeable. Also, whenever my A/C kicks on and I happen to be at a stop light, the car damn near dies. The RPMs drop from 1k to about 3 or 400 and the car shudders. Any ideas (besides take it for service, I'm going to here in a day or two). I just want to know if there's anything I should look out for or expect from the service guys.

[lain]

If you are is getting that low on the RPMs could be a compression issue...would defently have that checked out.