I have a 1989 F150, 300, M5OD, LWB, 2WD, 140000 miles. Fresh tuneup, A.I.R. plugged at head ports, EGR restrictor plate installed...did not help anything so will probably take off. Tuneup included throttle body cleaning, IAC cleaning, cap, rotor, wires, plugs, filters all fluids and such. Has done this once and now ever since. When you first start the truck...warm or cold...but worse cold. It will miss. A dead miss for anywhere from 10-45 seconds...then never again. Just when you start it. Then purrs like a kitten. Could I my cleaning and such dislodged some carbon and got into an injector maybe?? I have run some seafoam through the top end via the brake booster and some through the fuel. New fuel filter also. I do not guess it hurts anything...more less bothers me. But if it misses at startup...wether for a few seconds or all the time...something is amiss...the odd thing is it clears right up in less than a minute and runs fine. I have both cats intact also. Thanks guys!