I understand Art won't perform exhaust repair anymore.

If you're speaking of me, you're correct, but can't imagine where you heard it. I just replace everything, unless the damage is confined to one or two parts, like when Mrs. Art backed into a snowdrift and bent the rear muffler and S-pipe. But those two items had been recently replaced, so were not rust-welded to the axle pipe. All came apart easily.

It takes up a lot of space, but I've kept a complete kit on hand cat-back. It fits all the non-turbo cars we own. Getting the front muffler off of the cat's outlet pipe usually takes a dozen whacks with a 2# maul that leaves that front resonator less than pretty.

No use for rust dissolving fluids cat-back. Have soaked header nuts though.
--
Art Benstein near Baltimore

I'm so busy I don't know whether I found a rope or lost my horse.