terrible miss/backfire

whe i am driving it backfires through the throttle body and loses power i cannot figure this out could this just be fouled out spark plugs

Year, make, model, engine, 8th character of VIN, what's been done to the vehicle as far as repairs, SES light on? What DTC's are stored? We need more information to help you.

it is a 89 s10 blazer 4wd 4.3 L fuel injected replaced fuel filter,coil,spark plugs and wires, distrubtor cap and rotor

can some one please help

Induction, (backfire through the intake), can be caused by incorrect valve timing, incorrect ignition timing, excessively lean fuel mixture, or incorrect secondary ignition wiring. Check the easy stuff first: ignition timing, plug wires correctly in the distributor cap, (firing order), and fuel pressure.

i checked the firing order that is correct now how do you check ignition timing

Behind the carpet, under the glove box, next to the firewall, there is a single wire with a connector, unplug it and check ignition timing with a timing light. Sticker under the hood should give the spec.