I certainly am getting some improvements with the higher flow now that I'm at 2x stock power levels...how can't I be? The "hot air intake" thing....on my car, I have a large aftermarket bar/plate intercooler. Any increase in air temps above ambient to the turbo (which isn't an argument....that is 100% a fact as I've logged it with a temp gauge and there is a ton of data form an engineer that has a GTI and dose all sorts of great testing to empirically answer these iquestions) is more than compensated for my the IC so in the end, the air entering the throttle body isn't any warmer running an open intake like mine or the factory intake...they are the same. I am getting more flow which helps with turbo efficiency however that is partially negated by the slightly warmer/less dense air that the turbo has to now compress - which just means my turbo spins a tiny bit faster than if I didn't have it. So in closing, I have more flow, same intake air temps, and a turbo that is spinning a little faster. But...I have that awesome wooooshy boi racer noise that's worth it alone.
Some awesome quantitative testing on all of this:
www.mygolfmk7.com