Truck information:
EGR Delete
APR Head studs / OEM headgaskets
New oil cooiler & blue spring + new screen
Power max turbo
^------ 2.5 years ago----^

New thermostat
175 CC injectors

I noticed the other day that my coolant tank took almost another gallon after I just filled it about 8 months ago.. I had my injectors recently done so I'm not sure if that had something to do with missing coolant and the technicians that did it.. I found this out while I'm trying to diagnose a bad heater core.

I have no symptoms of head gaskets (truck was studded / egr deleted three years back). My only suspicion is due to the loss of coolant.

I attempted to due a block test with green dye that should turn yellow with exhaust gases present.. I got the opposite results. My liquid turned darker. Picture is attached. Should the fluid get darker? Would it be due to the exposed heat of the coolant? Did this test go wrong?

Attached picture:
Left bottle is exhaust gases after 20 seconds
Middle bottle is control / unexposed
Right bottle is after four minutes above the degas bottle.

I also attempted to put a T right before the degas bottles coolant return line and checked the pressure with a gauge. Running PSI with the truck warmed up with no load was around 5. It wouldn't run any higher unless I let the truck loose.

When I would pull a WOT from second to fourth gear the PSI would jump with engine load two to three seconds lagged. Generally, the PSI jumped anywhere from 4-10 PSI per WOT run, the most I could get was a 5-12 PSI jump in about 3-4 seconds. Not once did the PSI peak over 14.

While the PSI peak is OK, should I be concerned that my PSI jumps with the load when I go WOT