Also should not re-use head bolts. They are torque-to-yield just like automotive ones. Each time head is removed, should install new head bolts. Better yet, install ARP head studs for more clamp force, especially with 17+ lbs of boost.
BTW - I wish I had taken pics but when I replaced my head (warranty) I could tell by looking at the sealing lines that the head had "moved around" a little. The sealing lines (gasket lines on aluminum head and block) in some places showed evidence of minor breech. Once I installed the ARP head studs, the lines were very exact and very clear all the way around the head telling me the head was no longer "moving around." These 998s should not "use" coolant. If anyone has to top off their coolant tank periodically, and you can't find an external leak anywhere, guess where it's going? Once I installed ARP head studs, I never have to add any coolant ever.