re: spark plug question

[William.Elliott@mail.mei.com]

>> I was wondering what plugs work the best in your experience with the MB?
> I'm getting mixed signals re: Bosch and NGK.  If Bosch, is it best to
stick
> with the W7DTC?

<<A matter of debate.  At the moment, I'm running some single pole ones
as an experiment.  To date, we've used W7DTC changed at 8000 miles.>>

Phil:  Why are you changing the W7DTC's at 8000 miles?

 My reason for asking: My '85 UrQ  (obviously not an MB but: K24, IA stage
1, 14psi)
started surging/missing under boost with W7DTC's at about 7000 miles.
The plugs looked great, so I replaced coil/cap/rotor/wires, etc... and the
miss was still there. All turbo/IC hoses were good.
Replaced the plugs with another set of W7DTC's: miss goes away.

Now it's 7000 miles later and my miss/surging has returned.  Again the
plugs look great.
Is 7000-8000 miles the life expectancy of these plugs? Gee, I though my old
small block Chevy's were bad!  Do NGK's last longer?  Anything else I
should consider?

Thanks for any advice!

Bill Elliott
Lake Mills, WI
'84 4kq (fairly rough, for sale $500)
'85 UrQ
'86 4kq