1988 Volvo 740 engine cuts out

I have had the car for two months with no problem. Last Tuesday I was driving on the highway and noticed the odometer needle dropped off for a second but then came back. Later that day I decided to put gumout fuel system cleaner in the gas. I wasn’t having a problem, but I thought it could improve performance. The next day I started the engine as usual, but it suddenly cut out after three minutes of driving. I pushed the car to the side of the road and was about to walk home. But I tried the ignition and it started up. I thought maybe it was a fluke and later took the car on the highway. After about eight miles the engine cut out again. But after a few minutes, I was able to get it started again. I drove home, about 12 miles without a problem. The next morning I drove about ½ mile parked the car for an hour, started to drive home and the engine cut out about 200 feet from my driveway. Now I couldn’t get it started again. At first, I assumed the problem to originate from the gumout, that it had loosened gunk in the gas tank that instead of being dissolved, was now clogging the fuel filter. When the engine would stop for a few minutes, the pressure would back off, and fuel would be able to flow again. But this theory was shot down when I tested for a spark, and there was none. Looking on the web, I found similar intermittent problems of the engine cutting out. The consensus was either a faulty ignition control module, hall sensor or the coil itself. My question is: is the timing of the use of gumout fuel system cleaner just a coincidence? Or could it have caused fuel (pump) problems that effect the icm to prevent a spark, and when those fuel problems are fixed, the icm (not being defective) will now generate a spark? How can I test for these different possible problems?