How much mileage? Have you done a compression test? These motors are pretty robust. The lack of power and fuel burn could be something as simple as bad turbo hoses, air leaks, plugs, wires, etc. And the 86 falls into the bad wiring harness issues.
Off the top, crank sensor on the later yrs, none on yours. Can't remember if the 86 has the radio suppression relay.
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