Evening,

The previous owner has fitted a pd160 air intake and when I was cleaning the engine bay last week I noticed that the interface panel (skoda call it the air sleeve) between the slam panel and the air intake trumpet is actually taller than the trumpet, meaning fresh air is forced below the trumpet and into the engine bay. Is this right?

To tell if your intake allows air into the engine bay simply look through the air inlet on the slam panel and you'll be able to see a long thin section through to the engine bay.

sounds right, IIRC some air is diverted down into the engine bay. Some people have cut out a part of the bit you mention to allow more air to flow to the airbox

Known as the rain flap

I'd worry about forcing more air by modifying the intake..mind you more air in might be better