My son's 93 Z24, 3.1 is loosing acceleration speed on the highway.
He observered his catalytic converter glowing red about a month ago, so we assumed it was blocked and when we took it in to a muffler shop, they removed it. We were still having acceleration problems, so we have changed plugs, plug wires and now last night all 3 coils. He said it ran fine for about 150 highway miles, but now will not accelerate quickly, even with the pedal to the floor! His gas mileage has dropped as well. Any thoughts?

Fuel filter, injectors, fuel pump... check you air filter as well

Finally resolved the problem after changing plugs, wires and coils. It was the Ignition Module. Cylinders 1 and 4 where not even firing! My son and I had changed the coils - 3+ hour job with our skills and not hoist but didnt change the ignition module. Had a friend take it to his shop and he could put it on a lift. Of course he could change the module in about 15 minutes with his skills and access to the lift. All appears to be good!