If engine was fully warmed up then that's good
Do you have a voltage meter and sewing pin?
You need to test the TPS and MAF sensor
With engine off key on
Use sewing pin to pierce the center wire on the TPS
Set Volt meter to DC Volts
Put black probe on battery negative or alternators case, a good ground
Put red probe on Sewing pin
You should see under 1 volt, .69 to .99 volt is spec
If over 1 volt then you will need to adjust TPS, loosen it bolts and turn it to lower the volts, if it doesn't move you will need to adjust throttle plate using the screw on throttle linkage, looks like an "idle screw" but isn't.
If under 1 volt then proceed
With meter showing under 1 volt manually open throttle and voltage should start to go up.
At WOT(wide open) center wire should show above 4.5volts, 4.5 to 5.1v is spec
Voltage needs to be smooth when opening and closing throttle, no jumping or dropping
Put on old TPS and retest if there are issues with new one
The TPS is the "accelerator pump" for fuel injection
On a carburetor there was an accelerator pump, when you pressed down on the gas pedal this pump would squirt in extra fuel to compensate for the extra air as throttle plate opened, to give the driver instant throttle response until Jets could "catch up" to fuel demand.
TPS does the same thing
MAF sensor is slow to react to air flow, when you open the throttle plate air flow at MAF will increase but there would be a delay.
TPS going up in voltage tells computer to give that "extra squirt" of fuel until MAF can "catch up"
So slow throttle response could be TPS issue
MAF sensor test
There will be a light blue/red wire, use sewing pin in that wire, thats for Red volt meter probe
Then Ground the black meter probe, battery negative or ?
Start engine, you should see under 1 volt if engine is warmed up, idle under 1,000rpm
1,000rpm should register about 1 volt
Raise RPMs and voltage should go up smoothly, about 1.5volts at 2,500rpm
MAF like TPS is about STEADY voltage, no jumping or dropping
Answer from PMs
Clogged exhaust system will show up as speed/RPM increases, at lower speed and RPMs engine would be OK but as RPMs go up back pressure builds up in exhaust system because of the blockage, if exhaust can't get out of the head then new air/fuel can't get in, so power starts to drop off and RPMs are limited to the amount of exhaust than can flow out passed the blockage.
You said above 30mph you can accelerate so I would say no, there is no blockage
Working Cats and mufflers can't hurt engine performance, outside of their weight, lol
Rangers have a tuned exhaust as well, tuned for mid-range power