Shit man! The problem isn't exactly fixed....I don't get it now. Got a new radiator, a new T-stat, new water pump, fans are working....basically the whole coolant system is working. I got circulation now. But earlier today I went to go pick my girl up from school so I was waiting in the parking, it was getting kind of hot (I haven't used my AC since I picked up my car from the shop) so I put the windows up, turned the AC on...and a minute or two later I notice the gauge start to go up real slow. I was like WTF??? So I turned the AC off and put the heater on and it went down again. Later on I was checking it out and this is what happens:

-If AC is on, it'll start to get hot
-Even with it off...now for some reason I start to notice the gauge going up but the fans will kick on and bring it a little back down....but sometimes the fucking gauge still continues to go up!
-But, if I press the gas slightly and let it hover around the 1.5k range it'll go back down real quick...but when I let go it'll start to climb again.
-But when I'm acutually driving around I have NO problems.

What the hell could it be?? Is this a sign of a blown headgasket maybe? I was told I'd overheat easily if it was the HG, also, I checked the Oil and there's no water. Any help would be greatly appreciated.