[JLMounce]

Okay, that rules out distribution issues caused by a dual plane manifold. You could look into an enclosure which is supposed to help, but I'm not certain how or if that would even work with a FiTech.

Another thing that may help is larger intake piping. Increasing the tube diameter size slows down the air velocity and aids in keeping it from slamming into the back of the carb hat. To my understanding that's what typically causes the lean condition. However that's typically due to airflow signal through the venturies on a carb. The FiTech doesn't really care about that. Have you looked into a turtle for the plenum in your tomahawk?