this just started a couple of days ago, my 1990 GMC 1500 suburban snow plow truck, 350 Cu.In. TBI, looses ignition about 4-5 minutes after start up, (heat related??), then after 20 minutes or so it starts right up again, and repeats the problem,does anyone else have this re-occuring problem and which ignition component is the most likely culprit??.