umm....screwed up intake manifold gasket? actually, i'd take off your intake tube off the throttle body, start the car, and see what the butterfly valve does. if it's closed, but the car's still at max rpm, check your idle air control valve, fast idle air control valves. if it just falls open or something, i'd guess it's more of a mechanical problem, like your throttle cable, pulley, spring is disconnected....but yeah, i'd check that.