Unless your car is making so much power that your tires are spinning due to a lack of traction when you step on the gas, changing your relatively new Michelins for some other brand of tire won't do anything to make your car any faster.

And unless your car is pinging under acceleration, using premium fuel will not give you a noticeable increase in performance.

Sounds like perhaps just a good old fashioned tune up may help you out as much as anything. New spark plugs/ wires/ distributor cap/rotor, air and fuel filters, and perhaps even a new o2 (lambda) sensor could give your DL a noticeable boost in pep, particularly if none of these items have been replaced in a while. Also have the ignition timing checked and reset if it is found to be out of spec...

billy242
1980 242DL/GT