As Theodor lives outside, and will be ruthlessly started early on the freezing winter mornings, I recently got a used
thermostatic warm air intake, part number 6N0 129 608 C for VW Polo and Lupo:
^^ The long lead takes hot air from the exhaust manifold, the shorter lead on the left is the cold air intake, the right side leads to the engine.
I've tested it with a hairdryer and it works. It is a bit slow, but the internal flap can completely close either intake.
The warmer intake air will allow better FE, and shorten warm up times.
But, I need to hack to fit Theo. Here is the stock intake:
The main part of the device is angled nicely, so it should be easy to splice in:
Unfortunately the HAI leg is angled up instead of down, and the plastic is welded to the rest of the device, so it cannot be rotated (that would make it too easy). I'll have to cut it and attach metal plumbing.