vacuum gauge to solve idle issue

Steve I'll tell you what works pretty well for me on the idle screw ports is to shoot a little WD40 in each hole and then blow some compressed air through them.
It has solved idle mixture problems for me multiple times over the years.
When I got Stephanie's 72 Swinger all back together it popped and sputtered and died at idle so I opened up the carb to find a bunch for fuel line rust particles in it.
I rinsed it all out, but the air with WD40 was what cleared up the idle problems.
The WD just adds some substance to what gets blown through the ports inside the carb and carries junk out way better than just straight air.