OK, gotcha. If there is a physical difference in size, I can see why the combustion physics might get mucked up ... thanks for making it make sense.
I can also see the danger in getting a thread going on this ... sort of like the "do you think synthetic oil is OK?" maelstrom of inputs!
Talking about plugs makes me wanna go out and find that '99 S320 (long) I have been lusting for .... and, then I remember the discussions on $10K worth of electrical parts ...
1991 350 SDL (200K and she ain't bent, yet)
former 2002 E320 4Matic Wagon - good car
former 1985 300 CD - great car
former 1981 300 TD - good car
former 1972 280 SEL - not so good car
a couple of those diesel Rabbits ...40-45 mpg