Those 3 wires with the ulilux spade connectors look like a home made lead using 230v power flex?
Follow it back to see where the cable goes. Its not an Audi/VW cable.
There wont be an airbag connector on the Recaro. At least Ive never seen one in an A3 (S3) with an airbag.
When I had my R32 an slk230 and an C55 we played around a lot with 'pod' and original air cleaners.
Never saw any real gains other than the nice noise.
Im convinced that's all they do is sound good.
To each there own but I'm sure the original S3 box flows more than the car can use.
If it didn't...
Tyre pressures, tyre types, alignment /toe. All need to be set before you can really say anything re arb's
Start with tyre pressures . I have found 38psi all round to work for me with 325/40/18 Michelin PS#3.
Experiment one end at a time.
Also throttle lift/easing can change loading s a real...