i have an 87 chev 305 tbi 4x4 auto. it will start and idle ok and drive fine for about 2 mins when cold (live in wisconsin cold= 15 deg) but then starts to sputter and die. put it in N or Park and it will rev up just fine. put it in gear and it falls on its face. i have changed fuel filter, plugs, coil, wires, MAP sensor and checked the tps. i also checked the tightness of the throttle body bolts and checked all the vacuum lines. any help would be appericated. this is my plow truck and it snowed 8in in the last 3 days.