i think I may have isolated a likely cause of the very rich running of my 1990 240 wagon. There's a lot of gas in the oil, and after eliminating the FPR, I suspect the frontmost injector is acting wonky. I did the 'screwdriver stethescope' and the back three sound normal, but the front one seems to hicupp at the same time the engine stumbles. I listened to them all, back and forth, for about 15 minutes.

So, is there a diagnosing method I should use before I pull the rail and injectors out?

If I do go ahead annd pull htem, what should I be extra- carefull about?