I have replaced my slide-throttle TB with three 1-barrel TB's.  The slide throttle was problematic, and according to the experts, the p-port engine idles best with the throttle plates very close to the ports.  This resulted in my three 1-barrel design.  They're 46mm each, off a snowmobile, or seadoo, or something similar.   

One problem with the slide-throttle design was poor idle, partially caused by the primary injectors being upstream of the throttle plate (fuel pooling, etc.).  The 1-bbl TBs have an integrated injector bung downstream of the throttle plate, solving the fuel puddling problem.  It also takes care of mounting three of the six injectors.  I've only run the engine a little with the new intake, but I can already tell that this design has resulted in a better idle.

Another thing with the slide throttle was high actuation forces required to open/close the slide.  This was worse when at idle.  The butterfly TB's don't have this problem.  They have needle bearings for the throttle shaft to ride on, resulting in a very smooth throttle.  

So, we'll see how it works in flight soon.   

Mark