I was having my car retuned yesterday by Steve. It had some stalling problems and a bad idle, so i decided to just tune it past 10 psi, what it was tuned for last time. At 1 bar or 14.5 psi or 311 whp my coolant bottle just boiled over. The car is an H23 with the following:

Modifications:
-GE Sleeved block
-JE Pistons 9:1
-Pauter rods
-Ported intake manifold with secondary butterflies removed
-Portflow Head w/P&P , Titanium retainers, custom dual valve springs,
-ARP head studs
-Quaife LSD
-t3/t04b .63 a/r stage 3 super v
-SFP Manifold
-Hondata 3b w/p74/75 ecu.
-AEM fuel rail
-Aeromotive FPR
-Tial 35mm hybrid.
...and some other stuff im prolly forgetting

The head should be off later this week. I dont understand what is going on. This is the second time this has happened. Last time the head lifted at 1 bar as well but it was running stock head bolts. I thought it would be ok now with the ARP's.
Has anyone had trouble with keeping thier head on on thier H series? I dont think there should be any reason the head should be lifting/hg blowing at this low amount of boost.
Any thoughts welcome.