340 build No POWER need help w tune

You checked vacuum with gauge is it still handy?
If so have it connected always if possible as it will help tune,
actually see improvements or negatives.
At idle, any increase in vacuum is a good thing provided timing
limits are not exceeded.
Is the needle waving at you at idle this COULD be too tight
a valve or an issue with valve train flat cam etc.
I would be looking for a vacuum leak, booster drip, plugged
idle air ports.
My 340 with less cam duration 232* needed 18* degrees initial
timing. The idle air bleeds in my BG Speed Demon needed to be
decreased in size. The first call to BG netted me an initial timing
suggestion, I was there already. The next day an envelope
showed at the mail box four very small idle air restrictors for taps
later and I had an engine that idled like it should.
1.5 to 2 turns out on the idle screws.
The fact you are idling with
near 0 turns out suggests, idle air bleeds are restricted, fuel level
too high while running causing booster nozzle drip. Or the
HP Holley is designed with a very sensitive idle circuit designed to
flow fuel with radical cams at idle I don't think this is the case.
If that is the case you will need to modify the idle air bleed holes.
I would contact Holley if that is necessary.