It depends on what you consider to be 'backfiring.' If you have a large amount of carbon in the cylinders that's getting hot and causing early detonation when the engine dumps in fresh fuel and air into the cylinders (and thus causes an explosion that comes back into the intake), then you might be up for some carbon removal. -but I'm guessing that this is not the case.

If you hear popping or bursting sounds in your exhaust when your foot is off the gas and the car is coasting while in gear, I would guess that your idle mixture is off.

Good luck and God bless,
Fitz Fitzgerald.
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'87 Blue 245, NA 214K