Here's an idea. Two linkages attached to the factory bufferfly levers. One above and the other below, so that as one lever pulls (and attempts to cant off) the other would push. The two linakges would not be able to cant toward each other. Since the levers can only move 90*, you can mount the linkages so that they have maximum distance between the two at 45* (one on "top", one on "bottom"), they will not collide with each other and should hopefully still be able to provide enough angular force at 90* to fully open the last butterfly.


Or, alternatively, turn the TB's so that they all share the same pivotal line and attach the shafts. Then either use the lever on one TB and a different AoA for your TB cable, or use the lever/linkage assembly from the other ITB setup.


A rack and pinions would be ideal for the pictured orientation - if not clunky, difficult to implement, and expensive. :)

Just throwing it out there.

edit: when I say lever, I'm talking circular.