1990 Chevy Truck lack of power and back firing out the tbi

i received a truck to work on and the belt had been completely shredded off the pulleys and actually wrap around some of them. i did a tune up set the engine to tdc and lined the crank pulley to zero and restabbed the distributor the rotor was pointing towards #1 cyl. in the5:30 position and the firing order on the cap is correct but the tbi is backfiring and has flames coming out of it and the lack of power still exists. is there something i'm missing i need help.