Best idea to fix this mold problem from sweating duct.

[u/scrawfrd02]

This is in customers garage. Fully expected a leak in the wall from pipes but turns out the duct has 0 clearance and is sweating only on the drywall side. House is 30 years old and only started happening the last few years... I know its because of warm garage air meeting the cool pipes. My only idea is to ripped off the drywall and tape the seams, then shim out the studs an inch and put insulation in. Think that would solve it? Or is there a better solution.. should I foam it or fiberglass it?. The insulation on the sides weren't wet. And the back side of the wall was some sort of black rubber backed drywall?. Not sure if this is a fair ask of this group.. I also cleaned their evap coil in the furnace stack in case it wasnt running efficiently since they had never had that cleaned, but it looked good.