Mike,
Based on the RPMs you are registering with those propellers, it appears that all of the cylinders are making full power. I have never used a turbulator in my Moki and my two friends with high time Moki 250s have not either. All our engines (except mine now) run great. By great I mean they all pull their respective scale 32" or 30" three and four blade Solo propellers at 3500-3800 RPM on the ground (this is what we set our pitch for). I have never chased the #3 cylinder running cool issue. If the engine pulls like it should at cruise and full power, I don't care if there is a bit of chugging and popping at midrange and below. In fact, I love the chugging sound because it sounds awesome during a big Corsair or Thunderbolt flyby.
I think your engine is running fine Mike, follow your #2 option and quit driving yourself nuts chasing the #3 cylinder temperature issue. As Goetz has stated numerous times, "...do not unnecessarily disassemble a Moki radial..."