He has a 300E 2.8, that's a 104 engine. I believe the plugs you are recommending are for a 103 engine. The 104 needs the flat-ring type seal, the 103 has a tapered seat. I still believe the F8DC4 is the correct plug, and .032" (.8mm) is the correct gap for either engine. Torque spec on the 103 engine plug is 20nm, on the 104 with the flat-ring seal, it's 29nm.