Engine running rich after exhaust upgrades

I have 94 SC 5 speed, no bold ons-yet. I had a custom exhaust put on couple weeks ago. 2 1/2 downpipes into hi flow cats into flowmaster dual in 2 1/2 in to single 3" out back to Y pipe into 3" pipes to a pair of 3" twister high flow mufflers.
I have gone heavy rich on mixture, getting black soot in tailpipes. Slight miss under heavy acceleration. Ordered new plugs and wires, but no miss at idle.
Should I reset computer after exhaust change???
Need help getting pipes all dirty

You will get soot in tailpipes however a miss is not normal..A miss at heavy acceleration sounds like a plug issue to me but if it wasnt there before you did exhaust I dont know what to tell ya..Changing exhaust alone should not cause a miss

changing exhaust has nothing to do with miss, unless guy who installed down tubes pulled a wire when screwing with flange bolts. Just coincidental is my guess. Very likely due to plugs and/or wires so you are on the right track. No need to reset computer. If no change after new wires/plus, write back. l

Have you run the codes yet?

Did they disconnect the O2 sensors when they did your exhaust?

They might still be disconnected?