[wolf k]

44 IDF's on 331 small block with mild cam, 212 duration, 112 lobe separation. 20 deg initial timing, 140 mains, 175 airs, 55 idles, 65 pump bypass, F11 tubes. 12.6-13.6 air-fuel ratio through all ranges of operation. Runs great, plugs look great.
My issue is, while moderately accelerating in 1st gear from a stop, I get some minor stumbling and fluttering from the exhaust in the transition zone, 2800-3000 rpm. If I accelerate slowly, no problem. If I accelerate hard, no problem again.
My AFR meter is not indicating if this is a lean or rich stumble, it stays in the 11-13 range through idle to full throttle.
The Pierce Manifold tuning guide states as follows; the emulsion tube influence is more marked at small and average throttle opening angles and during accelerations. This sounds like where my problem may be.
I already have gone through many jets and different combinations to get where I am now. It looks like I need to start guessing at emulsion tubes. At $12 a tube x 8, I would like to start guessing in the right direction. Any advice on which one?