Last week I put my stang back on the road after sitting idle for 2 years. The first week I pretty much babied it around. Well last night I went WOT for the first time. When I let off the gas to go to 2nd gear the revs shot up to redline like the throttle was stuck open. It didn't hit a rev limiter but the tach was reading 6500 before I shut it down and coasted to the side of the road. I though maybe a broke the throttle cable or something. I checked the cable and it was fine. I played with the throttle mechanism and could hear it open and close so I know it wasn't stuck. When I went to start up the car the revs shot right up again like I was standing on the gas pedal. Luckily this happened a couple blocks from my house. I limped home by starting the car in 2nd gear keeping my foot on the brake to keep the revs down. Anyone have any idea what could cause this?