If this is at idle your ignition at idle may be too retarded (headers glowing and brake fluid boiling) you may be burning
oil under the pistons which bypasses past the rings.
They can't cope with the excessive blow by.
I cannot give much advise on ignition at idle for your engine, but I myself aim towards 16 deg - as much as the starter can cope with. (racing cars, like my buddy's M8F are set fixed to about 38 deg - which you can't crank with engine hot)
The more duration the cam has, the more you need. Else you burn mixture into the exhaust (due to cam overlap).