I converted my 0-360 RV9a from carb to FI back a couple of years ago using the AFP unit that does not require the return system. Works great and Don and his folks are very helpful after the sale. Don was able to tune mine to a point where all cylinders peak (egt) within .2 gph of each other.
The support after the sale was very good--and that does matter!
RV9a/ECiIO360/James Cowl/Catto Prop
Flying since 3/06 and still smiling!!!