The only way you tell if it's working is to pull the hose off that feeds the carb from the pump within your case and see if it drips every so often. You MUST premix a tank of gas and drain the carb of unmixed gas before you try this. A manual shows a pumps per minute test to perform or a CC's per minute to receive.
Honestly, Yamaha has a very reliable oil injection - I have NOT heard of many failures. But, they set it very rich to cover there butt on engine failures. Thats why most guys block it off and run Pre Mix.
EDIT - By the way, that injection won't cause your engine to run poorly - UNLESS it is suddenly WAY too rich at which point your engine will smoke and your plug will foul, or it fails, or clogs and your engine seizes from lack of lubrication - thats it bro!!!!!
All our government does is distract us while they steal from us, misspend our tax $ and ruin our country