We must have fitted and in many cases used dozens of the big ETECS by now so have a good handle on their ways.
Agreed, like any 2 stroke a good burn after a lot of tick over will help. A common problem can be the belief that putting a bigger engine on but only running it a mid revs will be better. Not always the case.
Carbon guard (sold by Evinrude) can be sprayed into the air manifold and if having done a lot of low rev work can make a huge difference. Cost retail about £7 a can.
As per other post a deflector pin on the injector can be fitted by an approved Evinrude dealer.
Lastly if changing your own plugs always re-gap before fitting (never assume they are correct). From memory 25tho on the Etec plugs. Most important though is that they must be alinged correctly with the injector.