I have a 1999 Triton Ute HK, 3ltr V6 Petrol.

Hi, I have a 1999 Triton ute HK, 3ltr V6 Petrol, auto. After a long drive 100k + the motor runs fine, until I stop the motor for about 10-15min, then it starts to miss and stall when driving around the city, once back on the open highway, it usually clears itself, and a way we go. Had it put on the dyno maching, came up number 3 coil, changed coils, no change, still showed number 3 coil, another test, came up air flow monitor on turbo, changed monitor, no change, next we changed the electronic distributor (little black box before the coils ) still no change. Also change both fuel filters. Have had this miss for about 12mths now, and 100 mechanics can not tell me what is wrong. Please help Mark