Hi everyone, I have a '01 Montero Sport 3.5L (V6), 2WD. I recently started noticing a loss of power during acceleration... it progressively has worsened. Now, the truck is too slow to drive.

I loosened the catalytic converter (in case of clog), so the exhaust would freely flow... to no avail.

The truck had set up for over a decade. We replaced all rubber hosing from the gas tank, including filter. We do have positive fuel flow into the injectors.

I am completely lost as to what I should check next. Any tips or suggestions are greatly appreciated!!!

 

Very obvious thing - check the air filter. After that, disconnect EGR control to see if it will change anything (EGR might be stuck). If still no luck, pull the life data from the system to see how everything is functioning. Hopefully there will be a clue there.
BTW, do you think it's the engine performance or transmission?