[jhirasak]

Jon,

You certainly need to correct the throttle plate positions for cyl 4 and 5 to match those of the other 6. Slightly twisting the throttle shaft on those carbs should set things right for your idle and slow speed running. However, after you make this correction and if you still have a lean surge in the cruise rpm range that you indicated earlier, I think that it is worth a shot to try a F7 emulsion tube, as recommended, before adding a 3rd progression hole. The F7 emulsion tube does not have any high holes like the F11 emulsion tube, hence it will be richer at the start of the main circuit transition. If you need a set of F7 tubes, I can send you some just to try.

Let me know where you stand after you have adjusted the throttle plate positions.

John