Engine Power

I have a '92 2wd. I use it to go back and forth to work (5 min commute) and to take the trash off basically. It gradually began loosing acceleration power maybe a month ago. Been working too many hours to look at it. The other day, I left work and couldn't hardly get around the flat parking lot. Reverse was the same. Engine starts and idles just fine. Replaced the dis cap and button, wire, tried injector cleaner, air filter. What else could it be? I'm going to go change the spark plugs shortly but don't have much confidence that that will help since it starts and idles fine.

Thanks in advance.

try moving your timing a little each direction, just to see what happens. Do you have any check engine light?