First the truck - 91 "V" series crew cab with a bone stock 350 (170k miles) The problem - on initial crank up (1st time or 10th time) the motor has a horrible miss. I can rev it up to about 2k and it will clear out within 10~15 seconds and perfectly smooth (the change to good is very sudden). The problem is worst with temp extremes in either direction and best (meaning less time to clear up) around 70* (almost nonexistant if it's rainy). While acting up I can see black smoke from the exhaust but this goes away also. I'm also experiencing very poor fuel economy. I have GM service manuals but the info given assumes I have a scan tool. I have a laptop but the available Win ALDL software I have found does not cover my ECM (it seems to be an odd part number do to the 4L80E application). I'm lost and don't want to just start throwing parts at it. Any help is greatly appreciated!