Flyazzfly

I have a 97 Geo Tracker with the 16 valve 1.6 and a 5 speed manual tranny... it cranks right up the first time every time and idles perfectly but when I give it gas it bogs down and drags before it revs up... it does this every time you come to a complete stop... it also bogs down really bad going up hills... So bad I sometimes have to shift from 5 to 3 to make it up the hill... I can be running 60 and before I get halfway up the hill it will drop down to 40 if I don't down shift.. it never spits or sputters or misses, it just bogs down and starts dragging... If I engage the clutch and give it gas it revs up to redline like normal but once I let off the clutch it just bogs back down unless I down shift, then it takes back off like normal... I have changed the plugs, plug wires, rotor, distributor cap, and fuel filter... all 4 plugs are firing... I have ran numerous cans of Sea Foam through it as well as Lucas Gas Treatment and it doesn't help... I have adjusted the Throttle Position Sensor to different positions and that hasn't helped... it has a cold air intake filter and the air temperature sensor has been relocated and the catalytic converter has been removed but the O2 sensor has also been relocated into the exhaust pipe that took the place of the catalytic converter... Could my injectors be semi stopped up and not allowing enough fuel to get to the cylinders? Or could my fuel pump be going out and not pumping enough fuel to the injectors? (Keep in mind when it bogs down under load I can press the clutch in and it will rev up to redline but when I release the clutch it just bogs back down and drags unless I down shift) How can I check each injector to see if it's working properly and how do I check the fuel pressure coming from the pump?
*note* It does not smoke or use any oil and it's only showing 115,XXX miles