You may be experiencing a case of CarburitisTweakisToomuchus.

Suggest going back to square one as delivered and making sure all is set up correctly. Based on who you bought it from, I would have to guess that the meeting blocks are set up in a pretty standard orientation and the IFR's are down low.

Maybe open up the IFR to .036 or .035 and begin the tuning one step at a time from original config. Idle slots not over exposed and base timing set to around 24-26 depending on what your motor likes at idle and floats set correctly.

Your AFR could be bouncing due to an exhaust leak somewhere, or your O2 sensor is shot/dirty.