I can feel the diff, easy. It's flat on the top end with the actuator disabled, and it has a happy soaring top end with the actuator working. You can feel the changeover at 3000, when the long skinny runners start running out of breath, and you can feel the change in the slope of the torque curve as the short fat runners come into play and the engine really starts to breathe. It's worth having working, IMHO. Worst case, I'd wire the actuator at halfway open...

The new model has different material in the bushings that is more resistant to wear and deformation under side load. I always wondered why you couldn't just machine some new bushings out of delrin or something similar, and counterdrill the inner side of the front and rear bushings and put an oring on there. The other real problem with worn bushings is the intake leak at the bushing, leaning out that cylinder. If you disable it for a wiggly shaft, seal the bushing with rtv.