I am not sure if this is tranny or engine issue?

I have 93 SE Accord w/ 140K miles on it. I was having transmission issues (D4 light would stay on). Took my TCU and got it repaired. I don't have the D4 light issue any more. So here is the problem


When I am driving the gears seem to shifts ok (2nd to 3rd gear changeover takes a while). While I am in 4th gear between the speeds of 50-60 mph, it seems like something isn't right. It feels like the engine is about to stall. The RPMs look ok, I don't see them bouncing. Once over 60mph, the car rides fine. If I slow down from 65 to 50 and try to go back up to 60, I have the same issue. Also, I think I am getting less fuel efficiency, though I had to fill gas only once and had to do quite a bit of city driving too.

So what could be my issue? Transmission or TCU or is my Engine going crazy?

Any help is appreciated.

 

sorta like an engine stumble under light throttle at highway speed?
Put the car in drive [engine fully warmed up] hold the brakes and bring the RPM up thru 1700.
If you feel the stumble doing that you have plugged up EGR ports.

The other thing that comes to mind is that possibly the trans is going in and out of lock up to much from a mis-adjusted pressure lever cable.
The Driving test is; go along a road under light throttle at 25 mph. Floor the gas, the trans should downshift to first gear.
Repeat the drive at 28 mph, when you floor the gas the trans should only go down to 2nd.