You described my problem perfectly, runs great/ runs losy/ runs great/ runs lousy.... no rhyme or reason to it. Had the timing cover seal replaced since it was leaking oil onto the crank sensor, that didn't fix it.... Finally, decided to replace the DIS module. Voila! runs perfect! No more check engine lights, no more hesitation, no more running on 2 cylinders.... The weird part was even though the check engine light would come on and the gauges would go nuts, it didn't set a code.
For $71.00 it has been one of the cheapest fixes I have ever had!!!
Thanks again for all the help this forum gives! especially to us 'old' guys who are computer illiterate!!
Dr Lance