Last week I took my Sapph out for the first drive of the year. At first it was indling a bit rough, but after driving it it seemed fine again. But on boost it developed a misfire, so I drove it home again. But just before I got home it really started to drive badly. I just round out it's running on 3 cylinders. Cylinder nr 3 isn't doing anything. I unplugged all injector plugs each at a time and at nr 3 I didn't notice a change in how it's running.

But how do I find out if it's fuel or spark related? I did take the plug out and that was almost completely dry. If the injector was working would the spark plug be soaked?

The car is running an MSD wasted spark setup, so if it was spark related it should be 2 cylinders having problems, right? That is assuming the spark plug itself and the lead are ok.