92 Blazer 4.3 Vortec running poorly

Hello,
My father has a 92 Blazer 4DR 4WD V6 Vortec 190,000 Miles..
he takes very good care of his truck, but lately it's been running like shit. I took it for a test drive and you can't get any power out of it. It seems when you press on the accelerator the engine back fires this will happen until you let of the accelerator. My father plans to do a basic tune-up. Plugs and wires. He changed the fuel pump, fuel filter, oil and trans fluid about 2 months ago, but I believe the last time the plugs and wires were changed was about 1 year ago. I also believe the truck is minus a tail pipe as the weld broke lose and he is currently in a battle with the shop that installed the new exhaust 6 months ago. I would really appreciate any ideas on what could be causing this?


Thanks, Rick

Does it have the vortec plate on top of the engine?

Is the check engine light on?

I'm sorry I made a mistake it's not a Vortec... No there is no service engine light coming on either.

Thanks, Rick