Loss of power when warm

I originally thought this was a transmission problem but have since begun to believe it is an engine problem. 2.4L DOHC.

Car runs and shifts perfectly when started cold. Idles well and goes into gear smoothly to leave home. After ten to fifteen minutes it holds gears a very long time and I must feather off the accelerator to get it to up-shift. Then I have to feather back on the gas or it will downshift again. After a long enough time it works its way all the way to high gear and doing the speed limit. Any hard accelerator is an instant downshift. To gain speed I must just slowly increase accelerator and let the vehicle speed very slowly increase. No codes. All fluids clean and clear.

Done so far:
1. Replaced shift solenoid and input/output sensors. Had TCM quick learn completed at dealer. No indication of a TCM failure and no codes.
2. Replaced plugs and wires. Did make it idle smoother and at lower rpm's, but did not solve main issue.
3. Replace TPS. No change.
4. Replaced MAP sensor. No change
5. Cleaned MAF sensor with proper cleaner. It is intact and no change.
6. Pulled IAC and it moves in and out, cleaned with spray and reinstalled. No change.
7. Pulled fuel rail, removed all injectors and used nine volt battery to open and spray carburetor cleaner through them to clean jets. New o-rings and reinstalled. No change.
8. Bought IR thermometer and measured temperature at catalytic converter (part of exhaust manifold on the four cylinder) and it was 338 at inlet and 438 at rear. Measured at what I believe is a resonator (is this correct?) And it was the same in and out and noticeably cooler than at the catalytic converter.
9. Disconnected front o2 sensor wire to default to normal rich/lean without o2 adjustment. No change. Also wanted to see if ECM was capable of throwing a code and it did instantly. Reconnected.
10. Used IR Thermometer to measure engine coolant temp at thermostat housing (didn't trust gauge which was perfectly center on temp) and it read 194 degrees after a long stumbling drive home from buying the IR.
11. Cleaned throttle body and replaced air filter. No obstructions. No change.
12. Removed PCV valve. Rattled nicely. Sprayed with cleaner and reinstalled.
13. Checked for vacuum leaks at all hoses with carburetor cleaner and no engine reaction.
Not burning oil visibly. Minor blow back at oil cap when running but not major. No coolant loss.

Could it be coil getting hot? Exhaust obstruction even though cat seems okay? Temperature sensor? Fuel pump? Running out of options here. I have no means to check fuel pressure but tank is full and dropping it would be tough. I have not explored that much because acceleration and fuel seems fine until engine is warmed up. Any advice is greatly appreciated.