Alright so I have a 2000 GMC Sierra with the 5.3 engine. I recently have cleaned the throttle body which was gunked up, and also replaced the IAC and TPS as well. Well after I did all of that I started the truck and it ran rough for a minute or two and it smoothed out. When I took it for a drive it ran horribly so I brought it back to the house and took off the MAF sensor and cleaned it really good. After that it ran great except for now the rpms hang when I rev it up in park at 2000 rpms for roughly five seconds. I also noticed that when I'm driving and I let off the throttle to come to a stop, it feels like it doesn't want to stop and I have to use braking more often to keep from rear ending someone. Now the thing that really threw me was it seems to be worse when the engine has a load on it like when I turn on the air conditioning. Why in the world would it be doing this??

Sounds like a vacuum line disconnected somewhere.

Alright what lines should I start with?

Start from the throttle body and inspect every single line in that vicinity. It'* possible you might have broke/cracked a line.

mikes probably right but i would unhook the battery to baseline the idle settings too