For the guys out of warranty, maybe someone can open up an EL48 and see what the difference is. It may be something as simple as a different size idle jet or transition hole - which might be easily be altered on an earlier carb.
If someone is going to check out the new carb, there are four things I'd be looking at -
Idle or low speed jet
Transition/air bleed holes
Metering spring
Size of the metering orifice under the needle
Any one or a combination of the above would affect the throttle response.
Throttle valve and the software. The valve and the software have been the only major leaps and bound changes from the EL44 to the EL46 and finally the EL48...............and wait for it................the EL50 carb specific wise.