Simply replacing 8-10 yr old engines given to us with brand new B+S 35 BHP. We checked out the 37 HP efi but decided to "Keep It Simple! Changing to the EFI would have meant wiring loom mods etc--- A few other running mods were undertaken ie a new design SS exhaust which after a "few hours" are both working well.
As ever the thought is- "Good So Far!"