sb tuning problems

You may already have the primary butterflies opened up into the idle transfer slots and dumping way more fuel then you need at idle and low speeds. If this is indeed the case you need to crack open the secondaries 1/4 - 1/2 turn so that you can close down the primaries.

You will need to reset your idle mixture screws if you open the secondaries. I would also look at add some more initial timing, but more like 16-18 degrees for initial timing.