Civic - Honda :: 1992 - Stumbling / Bucking At Highway Speeds

I have a 92 Honda CX hatchback, 5pd with 140k on it. Since I bought the car used about a year ago it's had a low speed stumbling/bucking issue. For the most part, it's only when driving slow and steady but occasionally at highway speeds it'll do it as well. It's as though the whole engine just cuts out for a second. Giving it more gas always brings it back but it's incredibly annoying, especially in a parking lot with a cup of coffee or something in your hand.

For starters, the rotor, wires and cap are all very recent. I pulled the ECU codes and it indicated #7, Throttle Angle Sensor. Bought a new one, calibrated it, reset ECU and drove on. No change. Car still bucks and the CEL comes on occasionally. At first, I suspected the plug to the TPS since it was loose. I pulled new wire and soldered directly to the ECU and TPS. No change. Of interesting note, when the CEL would come on, it seems the TPS falls offline and the car runs great! I disconnected it for a tankful and noticed my 40mpg/hwy go down to 25mpg. Completely unacceptable for a car so painfully slow.

Another observation, the stumbling doesn't start until the car warms up. Also, if it's particularly humid/raining, sometimes it won't do it at all. A lot of people have suggested the O2 sensor, distributor, fuel pump/filter. I don't have money to just start throwing at this thing and of many similar issues I've read of others with the same car, nobody seems to have a solid fix.

I've replaced the TPS, completely cleaned the throttle body and IACV, checked for vacuum leaks and even opened up the ECU looking for cold solder joints. It looks newer than new inside. Like I said, with the TPS disconnected, car runs great but the mileage goes south.