Been working this morning to get my carbs tuned.  The engine is a 2.9L with a Isky stage-2 cam, Dellorto DHLA40 carbs, Mallory Uni-Lite electronic distributor, using an adjustable timing light and external tach to tune.  Fuel press. set at 2.9 PSI.  Base timing set at 10 degrees BTDC, any lower and the car idles rough.  Idle is set to 1k RPM.  Would like to get it down to 800 RPM if possible.  Car seems to run very strong in the higher RPM range.

Symptoms - while at idle the middle and rear carb will occasionally cough/pop.  This happens more on the front throat of the rear carb.  While driving, I can feel the transition from the idle circuit to the main circuit, like the car suddenly gains extra power.   

What I have done - from what I understand the transition from the idle to main circuit should be smooth and not jumpy.  Since I was experiencing the carb cough I figured I needed to move my idle jets up so I went from 70 to 75.  This seems to have smoothed the transition from idle to main and so far no carb coughing.  However, it is now running very rich and is certainly noticeable.  I have tried to lean the fuel mixture using the mixture screws but this makes the idle rough.

Questions - At this point I am thinking I going back to the 70 idle jets and see if I can richen up just the two carb throats that were lean.  If this does not work, is it a bad idea to run high idle jets in just these two throats?  Just how smooth should the transition be from the idle circuit to the main circuit?  I could certainly live with the way it was with no complaints.

Once I make the changes above I will record the spark plug number I am using along with some pictures of the plugs after some high RPM runs.

 

Running different jets in different venturi is only masking the real problems, if it helps at all.
I think you have a couple of different problems.
I bet they're not balanced properly which will cause the idle problems, and secondly the main circuit isn't starting right at the limit of the progression holes so goes lean before the main circuit starts.
The bigger idle jets fill the gap there but it'll be rich during the progression phase.
Smaller chokes or perhaps changing the emulsion tube will get the main circuit to start earlier.
Which emulsion tubes do you have?