alright ive had crazy problems with my car latly. when i start her up sometimes itl jst die or hang at like 400 rpm. ill usually have to rev it alittle for a good 10 min or jsut drive it and like 20 min later or so itl go back to normal. and jsut yesterday it was doing it and when i went to give it some gas by hand (under the hood) it would smoke like crazy. im thinkin the smokes coming from a bad exhaust manifold gasket cuz i can hear the leak somewhere but would that mess up the whole idle/running condition of the car?