I have been keeping a spreadsheet of fuel usage for my bikes, and may be able to answer your first query.
Link to full post.
I have the IICE-Air units installed on both of my bikes; a 2002 R1150R with bags and BMW Touring Shield, and a 2005 R1200RT with a Hannigan sidecar attached.
Before installing the unit I had to run Premium grade fuel (93 octane) to control pinging if accelerating hard/suddenly; and it still did it on occasion even on Premium.
Running on Regular grade fuel (87 octane) I find that the bike still runs about the same as on Premium with the plug installed, including being less prone to pinging under hard acceleration.
As a bonus, the bike gets around 10% better fuel economy on Regular with the plug vs. running Premium before the plug was installed!
One HUGE difference I have found with the IICE-Air installed in the sidecar rig is when taking off from a stop. Because of the extra weight of the sidecar I used to have to give it a fairly large amount of throttle/rpms and feather the clutch quite a bit to get things rolling.
With the IICE-Air installed take-offs take significantly less throttle and feathering. Nearly as easy as on the 1150R solo bike. Makes riding the rig in city traffic MUCH easier.
For me, that was worth the price all by itself.