I've got an '87 GT, speed density system, that when its a little cool outside or damp, when you start it and take off driving will start to miss fire, backfire, have very low power, and just flat out run like crap! If you let it sit and idle for 10-15 minutes and warm up it wont do it it will run fine or if while your driving and its acting up you let off the throttle and turn the ignition off for a few seconds and turn it back on it will act okay. Anybody have any ideas on what the problem is this thing has been driving me nuts for several months now. I've checked fuel pressure, timing, i did a tune up on( didn't help). I cant think of anything else it could be!