checked sparkplugs and found spark plugs half black and half white electrodes
it looks to be a oil leak condition , intake leak ?
engine runs ok

Which plug?

What is the vacuum reading?

Was oil or water on the plug? Do you hear the engine miss at times when you start it up?

Water...that makes everything VERY clean...
Before pulling plugs mark which way up they sit in the thread.
Black on the bottom side indicates worn rings, Black on the top side indicates worh valve guides....
Black all over indicates a rich burn.. be it carb not sorted, PVC valve incorrect and or dirty
Too cold heat range... over advanced timing
Excessive white.. also check with magnifying glass for any tiny round metal beads...
mixture too lean, which could be scavanging from headers and/ or too much duration/ overlap in the cam, vaccuum leak or carb...heat range too hot

Also it is not uncommon on carbed V8 and V12 engines because of the longer runners to the end cnrs that these tend to run a little blacker... which it is normal to drop in a slightly hotter plug
As to tuning/ dialling in by spark plug/ tail pipe deposits .. on modern unleaded fuels, and espec with methanol added, is no longer a reliable option...

it is like some one divided it exactly in half . They are not totally black . Each plug was marked when removed and it appears to line up with the intake runners of the manifold ?

How many miles up on the valve guides?

heads are 3- 4 years old maybe 4/5 k

Any puff smoke out the back on initial fire up after sitting over night?
If so then definitely worn valve guides or stem seals.... is more embarrassment on fire up ...
Valve guides/ stem seals on a street car if machined right, should start to show plug signs around the 80K mark and start puffing around the 110K, and serious above that.. thu it is not uncommon for those numbers to be considerably higher with good maintance