2005 z71 suburban coolant and oil issues
 

I have a 2005 z71 suburban with the 5.3 Z-code engine with 210,000 miles on it. Its been puffing smoke at start up for a while and i started loosing antifreeze. I was guessing head gaskets but it never overheats and temps stay rock solid. I changed out the valve guide seals, valve cover gaskets, new water pump, plugs, wires, belts. after doing all of this things seem to straighten up, I wasnt loosing antifreeze anymore and the puff of smoke at start up lessened. after a few weeks i noticed a little smoke, steam coming from under the hood, this ended up being the T- connector that hooks the hose from the water pump to the heater core. I had replaced it a few weeks earlier when I done all the changes. I chalked it up to a faulty fitting. I replaced it and it stopped leaking. this morning while checking the oil level i took the cap off the recovery tank to check the antifreeze level and it was full. after driving to work i noticed smoke, steam coming from under the hood, i raised the hood and the same T was leaking. I took the cap off the recovery tank and it stopped leaking. So here is my questions,
1. could my recovery tank cap not be releasing causing to much pressure in the system?
2. I'm getting the smoke again at start up so could my head gaskets be blown? (still rock solid temps with no overheating) it maintains 215 degrees and blows hot and cold air on demand.

Welcome to the forum.
Have your radiator cap tested. Do a compression test on the engine. What color is the exhaust smoke at start-up?