i have a 88 350 tpi all stock and am trouble shooting the a rough idle and surging mostly when in park while warm and noticed 2 things that seem strange to me and hopefully some1 here can make some sense of it .

1 . while the motor is warmed up and starts surging , if you unplug any injector the surging stops and immediately starts doing it again when it is plugged back in .

2 . after running the car then shut it off , if you open the throttle body and put you ear next to it you can hear a hissing sound ..

 

sounds like a vaccum leak

 

sorry , maybe i was not clear in my post orgonaly . when i said you can hear a hissing sound i ment when the car was not running .