Watch out the multiple spark setups run awesome but not all timing lights will show a true timing below 3000rpm or so when the multiple sparks are happening.

So what I think might be happening is his idle feed restriction is too big. If that's the case then the idle screws will be less than 1 turn out for maximum vacuum at idle. Remember the idle screws control how much mixture is allowed to come out of the idle discharge, the air fuel mix is controlled by the IFR idle feed restriction size vs the idle air bleed size.

I stuck some guitar B string wire in my IFRs and was able to run the idle screws out from 3/4 turns out to more like 1.5 turns out. The added benefit is that the same fuel mix that comes out of the idle port and is controlled by the idle screws comes out of the t-slot which can be the primary source of mixture at very small throttle openings (like maintaining 30 mph with a 400 hp motor)