Sounds like you've had the car for a while.. please give us more info.

When did you get it?
Last tune up with plugs, wires?
Ever clean the throttle body? Perfect time to fix that coolant leak at the TB btw
Any exhaust leaks?
Any check engine light?

Personally, I like to fix the known issues and then go from there. Otherwise you are saying..these might be the problem and I haven't addressed the obvious yet.