My understanding is that the Karmann Vortex maf requires laminar flow to read accurately. The factory intake facilitates this flat, uniform air stream using a panel filter placed directly in front of the sensor. Doesn't matter where you place a pod filter, it's still not going to give the laminar flow of a panel optimally placed.
You are much better sticking to the stock air box and snorkel if you've already got them.
A lot of people like to run a secondary intake hose/duct into the air box that draws from somewhere a bit lower/cooler, but its not a requirement.
As mentioned, normal Pod filters do more harm than good due to the way they pull air through the MAF sensor incorrectly.
On our cars, the MAF sensor sits directly behind the air-box and measures the amount of air passing through it on the way to the engine using a combination of ultrasonic waves and black magic.
The unit is designed to have straight, even airflow running through it in order to get an accurate flow reading (which it can get from an air-box). Cone pod filters don't do that.... instead, they create a vortex of violent spinning air which just completely fucks the sensor up...
Saying that though... It's still entirely possible to run a Pod filter and a cold air intake without suffering any of the detrimental effects... its just more effort.
A cold air intake with a sizable elbow and large enough gap between the Pod and the MAF unit can minimize the vortex effect. You'll need to move the battery to the boot and get some custom pipes made.
It's also possible to run a Pod filter without a CAI. K&N make oval-shaped-units which perfectly match the oval shaped intake on the MAF unit. A good option if the car came with a cone pod and no stock airboxes were floating around at the time (my scenario). Then you've got issues with heat soak etc etc </ramble>"