I have been having issues with bucking and backfiring above 2,000 RPMs at cruising speed in my 88 Comanche 4.0l. After replacing and fixing a number of parts I've narrowed the problem down to the ignition. I test the coil and stator and both seemed fine. I wasn't confident in the stator test because it didn't have a range of spec values, so I disconnected the stator and took the truck for a drive. It ran the the same way it did with it connected. Is it safe to assume that is is bad?