Low power, poss trans problem?

I have a 2000 e350 with a 5.4 and an automatic transmission, under normal acceleration it shifts fine and moves on down the road. Under heavier acceleration it feels like the trans is slipping or starving for fuel, it never shuts off and runs perfect, trans fluid and filter changed, fluid looked and smelled great, no debris in pan.I have also replaced the fuel filter. could this be a TPS problem or is there some sort of cable running to the trans from the throttle plate that regulates pressure. The van has 178 k highway miles and has been meticulously maintained. Oil and filter every 5k, trans fluid and filter every 30k. there are no codes showing on my scans.

I would hook up a fuel pressure gauge to the rail and run it through the doghouse then test drive it and see if the pressure drops under hard accel.

Catalyst could be partially plugged and cannot handle exhaust pressures under heavy acceleration flow requirements. Converters are supposed to be replaced at 100,000 miles. You can drop the converter down at the front and tie the pipe up out of the way and see if you notice any difference in how she runs.