Did you change the plug boots on the coils? ( 3 of them )

Swap the # 6 coil for another cylinder and retest.

Coils can fail on both ends. This car has a waste spark system with a spark plug is on each end of the secondary winding. If one end opens up, both plugs won't spark. If one end is arcing to ground, the other end will still fire.

96 should have the good wiring harness.

I pull injector wires to test for a dead cylinder, however my 97 SFI ME 2.X it detects a miss fire then shuts off that cylinders injector. So, if you have a sometimes firing cylinder, it will go 100% dead after 15 sec and won't refire until the key is cycled.

I think your 96 has a older HFM system (2 or 3 ECM plugs Vs the 7 or so for 97 ) so it might not have cylinder shut down.

Lastly, there are 2 different coils for the M104 motor with the split sort of being 96 older HFM / 97 newer ME but the C class seems to have older coil overlap past 97 and the 4 cylinder gets mixed in too. Physically they look the same, I'm guessing it is a winding resistance change.