Just purchased an 04 Silverado and am having a couple issues
 

Hey guys I'm new here, just bought my truck yesterday. It's an 04 with 194,000 miles. I bought it knowing it had some transmission issues and I'm going to get those fixed but also it has an idle problem. I replaced the alternator today thinking that was it but it didnt help. When I'm in park the truck idles alright but once I shift to Reverse or Drive the rpm's drop and sometimes when I'm backing up the truck will die on me. Coming to a stop it feels like the truck is going to die also. Also with the headlights on the idle is bad but with the lights off it gets better for some reason. If anyone has had this problem could you please help me out? Or if anyone knows of this proble. Thanks.

Just bought an 04 myself. It's the 2500hd with only 67,000 miles. I noticed the same sort of idling issue, only not quite as bad (it wouldn't die). I cleaned the throttle body. It was pretty dirty. Then replaced the mass air flow sensor (you can clean them but for $80 what the hell. Finally I installed the 57 series K&N cold air intake. Now it has a very smooth idle and the the change in engine sound under acceleration is sweet.