Have a 2001 4

Have a 2001 4.3 l s-10 blazer, it spit and sputtered and shut off, while trying to start it, it was acting like the timing was off, popping through TBI. I have it a garage and they thought it was the timing chain and it wasn`t. They change cam sensor, crank sensor, they have spark and I sprayed starting fluid in the TBI and it still wont start, it backfires or sometimes shoots flames out the TBI, and also is there a spider unit in a TBI engine? Can you help me please!