the spark plug boots do cause problems even if they are visually ok. the ones under the coils particularly are suspect - not the coils themselves but the boot underneath. they cost less than $10 each if i recall. BTW, platinums plugs are considered a no-no on these engines. get the factory spec Bosch copper ones F8DC4 at the dealership (hard to find elsewhere). they are a fraction of the price of platinums and are tried and tested by almost all m104 owners on this forum...
1993 300e-2.8 - gone now <sigh>
"Do not adjust your mind, it's reality that's malfunctioning"