I have a 88 gt with the 5.0 engine I put 351w heads on bbk long tubes some type of regrind cam the car dont like to idle when cold and when it does warm up it will run good and strong for bout 5 mins then it will start running rich and start hesitating and popping back thru the intake something is shutting the fuel pump down it seems
You need to pull the codes from the ECM. Do a search for the Surging Idle Checklist. Follow the directions for getting the DTC codes first. That will point you in a direction to trouble shoot.
