I would remove, but that is MY opinion! Any Mercury I build DOES not get the oil injection put back on if they want a warranty. Evinrude and Johnsons on the other hand is the customers choice.
I had James remove my oil injection from my 95 Merc. 90 for less than 1/2 the price Sportsman on Bonny Oaks wanted to charge me. He gets ALL my motor work from now on.