I ran my electra EFI for about 1300 miles on the original Bosch plug. The bike ran fine once warmed up, but was reluctant to idle from cold until the engine had run for a couple of minutes. I changed from the original Bosch to the recommended NGK, and the difference when idling was like night and day. It will tickover from cold without help, and the tickover is generally much more even.
The other thing I noticed was that the Bosch plug (twin electrode one) looked far older than a plug that has covered only 1300 miles should. I have taken spark plugs out of my car after 10,000 miles that look better than it. From now on it is NGKs for this Enfield.