Well, I am impressed with these plugs. My 1987 260E now has a silky smooth idle, smooth acceleration and I now average 25mpgs.
I have picked up 3 mpgs overall. The car is a joy to drive. (as if it wasn't before)
I used the plugs IT16 part number (5325).
My impression, I love them. Well worth the money. They run great but the downside is that it is very expensive.
1987 260E Charcoal Grey 157,000 Miles
1987 260E Forest Green 120,000 Miles