I have a 96 Ford ranger, 4 cylinder manual and have a problem I can't figure out. I can start the truck every time with no problem it isles great and I can sit there and rev it all day no problem but if I go to drive it I can make it about 1/2 mile and then that's it, ill press the gas petal and it won't do any thing but kill the gas (no gas) but soon as I take my foot off the gas it will idle just fine and rev fine but won't go anywhere unless I let it sit for a few mins and it will start all over. I have replaced the IAC, TPS and today the external fuel filter that was clogged but same thing. Once in a while if I push the clutch in it will stay at a rev for a sec. Please help

Fuel pump...

Possibly clogged catalytic converter

Fuel pressure below specification, try hi pressure gauge, run pressure and volume tests. The filters can trap debris if you have it in the tank, it can wear the fuel pump. The debris that collects at the injectors can end up plugging even depositless injectors and they can need replacing. lets hope it is just a weak pump. During the testing, start and run the engine and remove the vacuum supply line from the fuel pressure regulator. the reading on the gauge should max out. the pumps ability should be 50. inspect lines for damage or pinching. when you step on the pedal, that opens the throttle, takes vacuum from the regulator. stops the path to the return line. there should be a decent volume of fuel being sent and the pressure increases. since yours can just idle, it says testing is indicated.

Catilytic converter.you have 3 it is the first one.l pulled mine off and beat with a hammer all stuff insde of it out.put back on runs great.

Vacuum line did this to my ford replaced vacuum line and it runs great