2009 LNF cobalt tuning nightmare

Hey guys I'm new to tuning but I managed 486whp on my last build. This time I added a ported head and some diamond 10:1 pistons and the maf is very hard to tune. That and the car seems to stay in open loop for what seems to feel like 10 mins when first started and runs like crap until it enters closed loop. No check engine light and drives fine when in closed loop. Just takes forever to exit open loop after initial start. Also when a new tune is flashed when the car is fully warm and restarted the car reverts back to open loop and stays there for another 5 mins running like crap. Feel free to chime in as im stumped. I've been advised to change my upstream o2 sensor as it might be on its way out or getting lazy and its 3 years old so ill do that first. Car got a new oem maf as well. Thanks dudes.