I ran a 14 tooth and a 16 tooth on my Polini kits, and the 14 seems likes its dragging too much, geared too low.
I have two port matched polini's, both with 15mm bings, one with Techno Circut, and the other with Techno Estroil. Both cases ran very comparable when I had bullet exhausts on both. I put the Estroil on one and the Circut on the other, and after jetting, the Circut exhaust bike needed a 14 tooth sprocket to keep up in acceleration to the Estroil, but it fell on it's face too soon, the engine was revving too high for low cruising speed. The whole point of this is to say, I'd say if you want more acceleration, get a torquey pipe like the Estroil, not reduce your gearing. OR get a 4 petal reed valve and 20mm carb! Wow! Of course, gears are 5 bucks, instead of $200+.