Did you ever resolve this??? I am having nearly an identical issue, with what sounds like nearly an identical rig (1993, 5 speed manual, 260k ish miles). Would love to hear what you ended up doing and what/if anything worked, before I throw more parts at mine.
So far I've tried both coolant sensors/senders and a fuel filter, to no improvement. Previous owner claims they tried spark plugs, plug wires, coil, catalytic converter, & O2 sensor (no receipts, but parts look new). Next up was going to be cap/rotor (and maybe try again on some ignition parts the PO claimed to have replaced), or maybe just a new distributor all together. Runs fine when cold, but after running for a awhile starts to stumble and misfire/backfire bad when you try to give throttle. Does seem to crank for a while to start also, which I'm not yet convinced is related, but maybe. And only other oddity is the temp gauge never comes off cold, PO thought thermostat was stuck open maybe, but I'm not planning on diving that deep until I fix the rough running and do a timing belt. Again, don't think this is related, but maybe...