First off, I'm happy to display my ignorance in public

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I've been so impressed with the results in using corn-free gas in all of my 2-cycle stuff (and really happy with the '90 carbed jeep rebuild) that I thought I'd try a tank in the pcar. Octane, of course, was lower (89...93 premium), and now I have about 2 seconds of dieseling at shut off. How come?