The TT scoops air lower down in the grill. It's not 100% identical to the GTI, however the new graph below was recorded on an Audi TT with the new TSI Valvelift engine. It's a huge improvement towards simplifying the entire system.For the Mk5/6 VW's I can see this, but when I was looking at my bay to see if I needed that breather hose, I found it interesting to see where the factory snorkel-looking thing terminates, that there's no opening to the outside. It is blocked (not sealed) buy grill shrouding.
Plus the TT hood "clamshells" over this area quite a bit. You're not getting the same ram-air effect that the intake may offer w/the VW design.
I have faith in the APR products (heck I ordered one) so I'm not stating this to shoot down anything. Just pointing out it is a little different. Would this affect the engineering data below or not?