I don't know if all this has to do with a bad temp sensor since I just replaced it last summer with the stock one, but aside from the heater not working everytime I keep my car at my shop's garage it's kept warm, when I take it out for a ride she runs real fast. When it's parked out in the street and freezing she is very sluggish.

 

So..you're saying when it's parked in a heated area, and you start it up with the engine cold, it runs fast...but when it's cold, it's sluggish? NORMALLY, the car should run faster when it's cold because the whole engine is colder and the engine bay where it gets its air is colder as well... But....hmm....are you running thick oil? Maybe when it's cold outside the oil gets on the thicker side and it's slowing the engine down...

 

Hmm... I forgot what oil viscosity I am using( brain dead), but yes when the I start the car in a heated area it starts up quiet and just runs faster but when I start it up outside the sound from the muffler it very loud and runs very sluggish. I gotta change my oil anyway what should the viscosity be?

 

Depends on how cold it is there....I'm no expert on oil weights.. I'm in Florida so it never gets too cold....I run/ran 10w30 year round in both the v6 and v8 and never had a problem with either. Maybe 10w40 might work better in the cold weather...I forget though....