88 GT backfire

is it an exhaust backfire? if so, your smog pump might be contributing to that (when the motor is cold, air is diverted to the back of the heads; once warm, air is sent to the cats).

unless it has not had any sort of tune up in some time, i would not necessarily think plugs would be a solution (unless they have been in there longer than the service interval, etc). you could pull one or two and see how they look or swap them all for giggles (always a good idea, IMHO. just dont hope that this solves the problem).

how is manifold vacuum? any leaks?

it shifts great the rest of the time and all that, right - not a kick down issue exacerbating another issue?

enough of my ramblings. good luck.

sgarlic said:

It sounds like the backfire is coming through the engine compartment. I think the plugs are past the service interval to be honest.. I'll change those out this week and see what happens.

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that sounds like a plan - if those plugs have been in that long, it is good to do even if it does not solve the problem(s). as i bet you are gonna do, i might give other PM items a once over while at it. good luck.