The shared intake ports allow complete separation of A/F into cylinders 1-2, 3-4, and 5-6... with 3 throttles, not 2.
Moving the carburetors apart is probably an improvement, but the 3-4 port is still fed by both intakes.
As to ratios: it's nice to know what number you have, but without individual sensors it's just an average, and no way to tell whether the cylinder-to-cylinder deviation is 1% or 20%. Even with 13.8:1 on the display any cylinder may be borderline lean (16:1) and knock under high load. You have to adjust for what the engine tells you, not a number. If all cylinders had the same A/F 13.8 would be way too rich for high vacuum cruising, 15 and up will give better mileage.
Does the Sniper have vacuum input as part of the fuel control? Are you using vacuum advance at the distributor? Adding advance without leaning the mixture won't help mileage.
Most OEM EFI pressure is 43.5 psi.
