More help please

[alfisti@domain.elided]

Hello everybody, please can I ask for some more help re 2.0l Alfa 
engines.  126k mile on the clock
New Air filter, oil and filter, spark plugs, leads and distributor cap / 
rotor arm.  Marelli electronic ignition using hall effect sensor in 
distributor.
Dell Orto carbs

The problem is this:  When right up to operating temp, everything is 
fine.  Lots of grunt, revs right up to 5k (wife imposed redline) 
without any problems.

When starting, always needs choke.  Sounds as though it's only 
firing on 3 cylinders for a few seconds, then evens out, but the idle 
is still very rough at anything below 1000.  Have raised the idle 
speed as much as I dare as a stop gap.  Even when hot, the idle is 
very lumpy, and sometimes, it takes a few seconds to drop to 850 
rpm.  
I have 1 problem that may be relevant:  A PO mashed the mixture 
adjustment screw on no 3 cylinder, and it cannot now be adjusted.  
Can this be removed using a stud remover, and easily replaced, or 
do I need to source one form a carb shop?  Would this cylinder 
being un tuned for 4 yrs running cause the problem? Can I fix it in 
the way I have described, or is there a better way?

Other things, possible air leak?  Where would this be most likely, I 
can't see anything around the manifold, but any tricks would be 
appreciated.

One last thing?  There appears to be very little suck from the 
vacuum hose to the vacuum advance unit.  If you plug this with 
your finger, then you can *just* feel it, but no more.  Is that normal, 
or should there be more suck.

Thanks in advance

Catman

Tyger, Tyger Burning Bright
116 Giulietta 2.0l

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