Recently had misfire troubles with 3.5 v8.
Tracked it to the plugs which were blacker than black saturday.
Decided the mixture was too rich which would explain the excess fuel usage.
Evened that out a bit and all was well for a a good few thousand k's.
Yesterday i encountered the same symptoms
pulled the plugs today and discovered mixture is still too rich (now adjusted).
But i also noticed that the plugs on the left bank (looking at windscreen) were alot cleaner than the ones from the right bank.
simple fix if only i was running carbies.
is there a way to adjust each bank seperately myeself given the EFI?
Or do i need to go digging in my piggy bank....