Engine Vibration

I noticed that when the outside temp is warm (i.e. 70+ deg), my 4.8L Vortec runs smooth. But when it gets colder out ( I live in northern Ontario ) I get alot of vibration out of my motor. I checked my iat sensor and it is fine. Could this be an air leak somwhere on the intake?I am not hearing any sort of vaccum leak anywhere. Any input would be appreciated.

Pull any trouble codes and check long term and short term fuel trims. This will tell you if you have a leak.

I had a 99 Explorer that did the same thing. Whenever it got cold, the intake manifold gasket would shrink causing the engine to run real rough. The dealer replaced the intake manifold under warranty.