My car has been throwing a p0200 injector malfunction code. After I reset it it keeps coming back. So today I did a ohm test the #7 injector does not respond, all the other injectors show 13.2. So I am guessing that I have found the problem. The one thing that I am curious about is the #5 & 7 injectors have some corrosion where the connector plugs on to the pins. I cleaned the corrosion and scraped the pins with a file and I still am not showing any reading. What would cause this corrosion? Also since I have already had tuning should I just go back with stock injectors or should I upgrade? Thanks