Have a 2011 lml experiencing low coolant. First started after driving a couple hundred miles knowing the coolant level was where it needed to be. Gradually got worse over time, but no change in performance. Recently had a large drop in coolant but the truck had been sitting for a good while as it’s not my daily. The truck is deleted with egr blocker plates and no other modifications. Checked oil cap and had an oil analysis, no coolant in oil. No puddle underneath truck. Check upper radiator hose for hardness after running and I could still squeeze it. Only other thing I could think of is that the coolant is getting into the exhaust. What else should I be looking for or what else can I do???