It sounds like it could be the ignition coil. Typically the ignition systems are very strong. I hate to have you keep throwing parts at it. Disconnect a plug wire and put a spark plug in it and ground the plug and see if the spark looks strong.

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1990 190E 2.6
1996 Grand Voyager 3.3
1985 Mustang GT 5.0 5 SPD
1982 Suzuki GS 750T