[W126 Coupe] HELP! resistor vs. non resistor plugs

[Tom Oelsner]

This afternoon I replaced my plugs to see if I could smooth out my idle that
occasionally ran a tiny bit rough.  RH...you cannot use Rapid Fire #4 plugs
as they have a one piece top that does not mate with the Bosch wires.  Also,
AC Delco says do not use any anti seize lube on threads...

So here is my problem.  The parts store did not have W9DC plugs in stock but
had WR9DC (resistor built in).  I queried him really hard about them and he
said they would be fine and would not impact performance.  So I gapped them
to .040 and put in new ignition wires (even though the old ones were only a
year old, I broke one pulling it.  So I replaced all.).  Well the car idles
really badly.  This is in spite of the fact that 3 of the older plugs were
really fouled.  So my question is obvious.  Are the resistor plugs causing
rough idle problems?

Tom Oelsner
90 560SEC