Harbor Freight sells something called an in-line spark checker - normally $6 each, presently on sale for $3. You hook them up between the spark plug wire and the spark plug. They create a flash as the spark goes to the spark plug. Buy 8 of them, hook them up, turn off the lights, and you'd know absolutely positively that you were getting good spark to all 8 plugs, cold and then hot. Of course if you were having an ignition problem it should show up on the DI, pin 17, but I find it comforting to actuallly watch the spark go to the plug.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=36258