Coolant Pressure build up 2008 6.4

For background, this truck was deleted, studded, new heads, and new turbos all within the last 15k (currently around 175k miles).

Right when I thought everything was fixed with this truck, I started getting excessive coolant pressure that will blow out pressure cap as soon as engine gets up to temp. Engine coolant is not overheating. Did exhaust gas test on coolant, with results not showing any exhaust gas in system. System also seems to build pressure when wastegate opens, but I bypassed wastegate to test and it still would build pressure. I would still have to guess its head gaskets, but I’m hoping anyone has an answer that doesn’t involve tearing this truck apart for the second time in 3 years. Weird to me that I couldn’t get any exhaust gas to show up in tests too.