On a proportional level, quite a bit. However the complexity is increased exponentially, and the electrical load has to be carefully planned and provided for.

For ec121,

The effects of the reversed 3w snorkel needs to be catagorized a little better. Most drones are "pusher" configurations, with the propeller aft of the carb. Turning the snorkel around is not influenced by the propeller really, un less one wants to factor the possibility of a low pressure area between the prop and the carb. In this cae we're dealing mostly with ram air effects. The increase in rpm may or may not be linear because they are generally notable at peak rpm levels with the aircraft in flight. You would need to first note the baseline performance of the engine on a dyno and verify the fuel map before turning the snorkel. Then turn the snorkel and check all the standard parameters once again to see the effects of increased air velocities at various airspeeds. Nothing really changes at zero airspeed, only with the aircraft in motion. Again, the propeller does not have a significant influence in this instance.