Stuck Idle??/
 

i have a 91 mustang gt, it is vorteched and has a little bit of work done everything was fine up intill last night the idle starts to stick at like 2000 rpm's when you push the clutch in and coast in neutral??? any ideas, and when it sticks it doesnt stick for too long it calms itself down after about 30-45 secounds sometimes a lil longer, but also if you put it into first gear and let the clutch out a lil bit to drop the idle then it is fine??? any ideas??? thanks for the help