I am in the shop now. 18:1 with twin 625 turbos (both the big ones) got 330K with 770HP and 2400Tq to the rear wheels. Never had any issues until last week, losing a gallon of water per day... Pulled the head, its junk, number one cylinder has been bouncing. I used all genuine Cat parts, updated head bolts etc... Im now learning that I should have gone with 16:1 pistons in the first place. Im a big fan of twin turbos because you get more volume with less pressure (pressure equals heat) I had 42 PSI all day long, never saw the pyro go over 900 (my powder coated hot sides look like new). All good, except that the head gasket will never survive that kind of cylinder pressure. Cat keeps recommending all sorts of band aids to "fix" the Acert head issue but bottom line, the high compression needed to meet EPA requirements is just too much for the technology they put into the head and head gasket design.