Hello, I have a 67 230 with dual Zenith carbs. I can not find any documentation on how to adjust them. My car is running rich (I think, from the smell) and it hesitates when accelerating from an idle. It also backfires when slowing down with the engine. I have the idle at 730 RPM and 1º BTDC. Any help would be most appreciated so I can get back on the road.