1986 Toyota Cressida unknown problem

I have a 1986 Toyota Cressida station waqon and recently installed an engine from a 1984 Cressida wagon.
When driving the car I have what appears to be a misfire. I have put in new plugs, wires, distributor cap and rotor and installed a new fuel filter prior to having the engine put in the car. Also installed a new coil on the advice of a mechanic.
When I put the car in park or neutral I can rev it up to 4-5000rpms and it's nice and smooth. But when I drive the car, it starts to misfire.
The engine I put in the car had set up for about 4 years and I'm wondering if the problem might be with the fuel injectors? Would the injectors have different requirements when driving and when I put it in park and neutral and rev it up?
I've run 2 cans of injector through 2 tanks of gas with no change in performance.
Thanks for any help or advice you can give me.
Ken