I NEED HELP! 1990 2.4l

i need help immediately, i am attending college to become a diesle tech, i have a 1990 mighty max that i got for free last year, the truck ran fine and had no problems. feb. i lost a water pump and cracked the head, i recently put it together and the truck runs horribly, the main problem is i have no power until i get up to about 55-60 mph and then the motor kicks in to full power, i tore it down and checked the timing belt, it was loose. could it possibly have jumped a tooth and thrown off timing? i also have horrible engine vibration, shakes the whole truck and the truck wants to die when it is in gear and lunges bad too? these motors have balance shafts could that have been thrown out of time as well. i need help i go to school 5 days a week and i drive 65 miles to get to class, this needs to be fixed pronto. i am open for any suggestions. here are some facts

-96k miles, i have put 5k on it
-timing is as accurate as i can get it aka finger in the hole trick
-i have no time to tear it down all the way and start over
-new head gasket 500 miles ago, along wth refurbished head
-no power until 55-60 mph then full power
-TPS was checked has no problems
- engine light came on 5 min after i put the head on and started it
- Auto trans
-4g64 motor
-ECI(electronic controlled injection/ignition, i dont have the book so i dont know)


i need this info asap, i have class and the truck is also eating gas like a 4x4
i spent 60 bucks in 5 days on gas.

i need help anyone please

-dieseltechrook

First thing you need to do is retime the motor. Not sure if this is an interference engine or not, but lets hope it's not. I personally used the timming marks in front of the motor and pulleys to time it, I didn't do the screw driver in the hole method and I had no problems. I will try to see if I can possibly get my instructions on the net to send to you.