Why does my MAF start working when I "tap" it?

[brookspw]

Been having all kinds of surging/rough idle/bad mileage issues. Checked vacuums, fp regulator, purge valve, etc. MAF replaced in march. Ran fine for a month or two then back to the same.

Car was surging at idle, I was looking for vacuum leaks, I said "What the heck" and tapped the MAP body right under the connecter. The idle immediately increase about 2-300 rpm then settled into a perfect idle.

This will last all day sometimes, other times it will last 5 minutes. But...amost always I can make the idle smooth out by doing this.

I have checked the connections, wiring, seal, etc and all seems fine. Is this just a MAF with a bad connection or something inside it or is there something else I should check?

Seems like I found the problem...but don't know which angle to approach it from.

Advice?