A/C question - '81 240D

[Big J]

There is a metal pipe across the front of the engine that is part of the A/C system. This pipe gets cold when the A/C is run. There also used to be insulation on this pipe. The A/C works fine, I secured some grey foam pipe insulation on that pipe and I don't know if it's my imagination or not, but the A/C seems to be cooler.

What function does this cold pipe serve and does the insulation make a difference to the air temp from the vents?