98CV_24

Hello, I am new to the ford world, and bought a 98 FCV with 150K runs excellent the intake manifold has been changed since the original one leaks. 2 days coming home from work I stopped at the red light and all the sudden the engine revs high as im in gear holding the brake down. the motor stays revved up about 2 to 3 K RPMS the car ran perfect before hand and all the sudden it just startted idling high please help Thank You