1990 Pontiac Bonneville Fuel Injector problem

Electrical problem
1990 Pontiac Bonneville 6 cyl Front Wheel Drive Automatic unknow miles

The first fuel injector in the gas line (back right) doesn't work most of the time, but sometime does. By using a noid (sp?) Light my friend discovered that the problem was electrical and not the fuel injector itself. The only problem is, we don't know what it is. My friend believes that its the pigtail, but im skeptical. I don't want to spend the time and money relacing it if its not going to work.