Any furnace/HVAC guys here?
 

When we had our pre-purchase inspection done, one thing the inspector noted was this spot on the furnace where the COIT guys had cut the duct open (see arrow), then closed it back up. He said there should be a small-ish hole there for proper air flow, but that seems a little odd to me, this being the main heat duct. Opinions, anyone?

Attachment 23187

There shouldn't be a hole there. There is no need for the heated air to be mixed.

On a side note, that looks like the original furnace that was installed when the house was new (probably 40 year old Airco, which are incredible energy-inefficient, probably 50% efficiency). It would be a good idea to have an appliance tech to check and make sure the heat exchanger isn't damaged and leaking carbon monoxide.

The inspector is on glue.

If you had a hole there it would just puke air out into the basement, and lead to a pressure loss in supply to the rest of the house.