Chevy 510

I have a 1998 chevy s10 2.2l 4 cylinder truck. Iv'e tried many auto repair shops and they just can't find the problem. The thing is that the truck has a "loogy" movement. Trying to overtake a vehicle just is impossible. It has a very high engine speed or acceleration speed. Just to get up to 40 mph it would take about a mile or more. The pedal must be pressed all the way to the floor before you feel some sort of overtake power. Nothing much actually. It even struggles to climb hills and does poor on fuel.I've changed o2 sensor, changed timming belt and put it to timming, replaced fuel pump, new spark plugs, changed transmission. Went to get it scanned. It only had a knock sensor and temperature problem. Any help? I'm desperate please respond quick as possible. Thanks