One white plug does indicate a leak to that cylinder somehow, although as
cylinders are paired that's not strictly logical, unless it is on the No.1
side of the gasket which would affect No.1 more. However vacuum leaks
usually tend to be 'stable', not come and go like electrical problems. The
HT tests are really only valid if you can reproduce the problem with a
timing light connected. You say it only happens at speeds over 45, but
engines are usually rev affected not speed affected. If it happens at 45 in
top, how about the same revs in 3rd? And 45 in 3rd as opposed to 4th?
----- Original Message -----
> I'll try to incorporate other suggestions in to this reply too. I found
> myself to be shockingly tired all day yesterday, so I didn't get out to
> do a whole lot of troubleshooting.
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