Check Engine Light On problems of the 1999 BMW 323

At approximately 64,000 miles the engine began running poorly. Engine would quit when accelerating from a stop unless the clutch was slipped and would misfire intermittently during acceleration. After a hundred plus miles of driving the engine warning light illuminated. A check of the fault codes indicated misfires on cylinders no. 1, 2, & 6. A check of the ignition system revealed vertical cracks in the insulators of all six, 100,000 mile, factory BMW ngk r5 spark plugs. This problem was reported to service departments at both BMW northwest & BMW seattle. I was told by both that BMW would not help.