i have been rehabilitating a 1990 Mitsubishi Mighty max with the 4G64 Sirius 4 cylinder engine. It has been suffering from a rough idle and bad drivability which i have narrowed down to a fuelling issue. I pulled the fuel rail and placed all four injectors into plastic bottles then cranked the engine a few times. Each bottle had the same amount of gas in it except number 4, which was basically dry.

I just paid $85 to get all four injectors ultrasonically cleaned and im still having this problem. I am beginning to suspect a wiring issue somewhere. what should i do?