I start my 91 Camaro rs 3.1L Rpm fluctuates from 1000 to 2600 for 30 seconds then calms down to 1000. Tried to drive down the road put it in 2nd gear and rpms shoot to 3000 put it in nuetral and the car keeps trying to accelerate and brake turns rock hard. Eventually it calms back down but the second i throw it back in gear it does it again. Car was dying on me before so i gave it a tune up. Not my first time giving a car a tune up so i am pretty sure i did it properly. I also replaced fuel relay and filter. Fuel pump had been replaced about 5,000 miles ago but i noticed some of the wires and plugs for it had what looked like bad or loose connections so i redid those. I am thinking either ECU,Throttle body, or Throttle position sensor. PLEASE HELP!

 

Check for vacuum leaks around the brake boaster hose.