Mother

Maybe check heads/valve area for cracks with zyglo or some non destructive test (once of prevention thing).

logray

Thanks. The heads were pressure tested about 1500 miles ago and there were no cracks.

Flat6 Innovations

Were they pressure tested at temperature??
Makes all the difference in the world with M96 heads. I have even been bitten in the *** with cold pressure tests.

Spend some money on the heads, or you'll be back inside this engine again and sooner than you want.