accord lagging

My 90 accord drives great at times. When i'm driving and get to 2nd or 3rd gear the car seems like it has run out of gas. With my foot on the pedal it tries to hit the next gear (and starts fluttering like it's not getting gas) but prolongs unless i hit the gas to the floor. Then if i take my foot off the pedal and put it back on it will do the same thing. this only starts to happen once the car has warmed up. what can my problem be?

I'd change the fuel and air filters if it's been a while just to eliminate that aspect.

But only happening after warm-up hints at a closed loop (full feedback fuel management) problem...

Several items are disabled when the engine is cold, EGR, torque convertor lockup, o2 sensor is ignored, etc. Any one of those or more could cause this kind of problems.

When it starts acting up does it buck violently, or just sag and lose power, or rhythmic misfire, or something else?

Many things can be happening here...but a shot in the dark, it sounds like it's losing power which accounts for the prolonged wait for upshift (it's trying to stay in powerband by holding the lower gear until you hammer on it).

Anything from low fuel pressure to retarded ignition/valve timing to a partially clogged cat convertor can do this.

How's the engine temp? Normal? How many miles on this car? When was the timing belt replaced last? Did this come on suddenly or has it been working up to it for a while?

so far the fuel and air filters have been changed since it started. also the cat has been changed. when it flutters (or sputters) and the car starts slowing and once i floor it it gives it gas and speeds up. the sputtering isn't bad unless i just keep the pedal at top level instead of flooring it. engine temp is normal and it has like about 195,000 miles