You need to make sure air is out of the system as this will cause head to overheat which could cause cracking or best case scenario a blown h/g.
As Johnny said above, this time of year especially you are likely to get some form of condensation especially if the car is only doing round town short trips and not getting up to required temp to burn off any unsavoury deposits in the oil system.
When you did comp test did you remove all plugs at once or one at a time?
Also if the engine is forged have they used arp head studs by any chance?
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