You mean you added the 4-5 oz of sugar that would have been for priming, right? Since you're going to force carb with CO2 and not add yet more suger the difference will be the same as if you had just naturally carbed in bottles or kegs - i.e. negligible. You probably added 2-3 pts to the gravity as is always the case with naturally carbing, I really wouldn't worry about it thinning out or changing the beer.