i think the thing with the oversized kit. it downsizes right before the MAF sensor to the same size as the normal kit anyway so surely thats defeating the point ?
It has to downsize for the MAF to maintain the correct scaling. It also reduces further to get in to the turbo which has an inlet of around 60mm from memory. This is beneficial as the reduction (if gradual and tapered nicely) increases air velocity in to the turbo. The issue is the length of the narrow section - Think back to the 1.8T days and the huge turbo intake pipes that were developed and the gains they produced - the best performing ones all had the same thing in common..... The diameter was a lot larger than OEM until as close to the turbo as possible before tapering down to the size of the turbo inlet....
Another example with straws.....
Blow/suck through one and see how difficult it is: Oversize example (you can add a larger diameter one too if you like to simulate the larger diameter section of the pipe, but the effect will be minimal as the restriction is the length at the smaller ID (70mm)
Then:
Stick 3 or 4 of them together (much longer length at the smaller ID diameter - equivalent to the 70mm smaller/non-oversize version) and see how much more difficult it is...... The shorter the restrictive part is the better.
Primary school science 101 lesson over.
If interested though guys there's a wealth of info on the web in terms of fluid dynamics and frictional losses. I'm no physics expert but the basic principles are easy enough to understand
