Jetting Webers on 2.7 911 engine., Tuning. Options

[914Toy]

I recently installed a "double" Innovative air/fuel (A/F) gauge with sensors in both headers of my 1977 2.7 911 engine, which is stock except for: ignition, Weber carbs, reground cams (modified SC) for spirited street performance with the carbs, and exhaust headers (MB911). The A/F gauge has assisted final tuning, including fine balancing of the carbs (well worth it).

Ignition is Clewett crank fire with ignition timing set at: 10 deg. idle 800 rpm, 29 deg at 3000 rpm, and 33 deg at 6000rpm.

Carbs are Weber 40IDA's with 34 main chokes and tall secondary chokes. Jets are: 145 main's, 180 air correction's, F3 emulsion tubes, and 60 idle's.

Engine is running very smoothly at all rpm's, no carb "spitting" or exhaust popping, no hesitation under any acceleration, and instant accelerator response with plenty of power. In other words, running great. However, A/F's are not perfect with 10.5 at idle, 12.5 to 13 at cruising, and high 13's up hill WOT. On a recent uninterrupted 180 miles run on 101 at 3400rpm (78mph), fuel consumption was 24miles per gallon (IMG:style_emoticons/default/smile.gif)

I have discussed the A/F ratio issue with several carb "experts" - mostly Old School guys. Consensus is my numbers are as good as it gets vs. near perfect 14.7 A/F one can expect from EFI.

Any comments will be welcome.

[914Toy]

Update:
After much reading and testing ideas to discover how to increase my idle A/F's up from 10 - 10.5, including increasing the idle air jet orifices from 1.10mm (stock) to 1.18mm, I found the cause of my issue yesterday.
Previously I had found best idle setting with the idle mixture screws turned completely in (basically closed)? This means that fuel must be entering the throttle bodies from the intermediate orifices in order for the engine to idle. However after several inspections, I could see that the throttle plates were correctly positioned at idle, with their edges covering the lowest intermediate fuel orifice.
Cutting a long story short, with the carbs back on my bench, I observed that the idle mixture screws with "cup"washers covering O rings restricted the screws from being fully screwed in, leading to the previous conclusion that the screws were fully screwed in - closed. After removing the washers and O rings, the screws could be screwed in an additional approximately two turns! I reassembled the carbs and installed them with the mixture screws turned open one full turn. After unsuccessfully attempting to start the engine, I opened the mixture screws one half turn and the engine started immediately. After adjusting further to best idle and allowing the engine to warm up, the idle A/F mixture gauge showed steady 13's - success!!
I have since learned that my Weber 40IDA's were original equipped with mixture screws that did not have these cup washers and O rings. Here are two pics of the mixture screws: