Thought I'd update this. Ran filter for month and a half, no problems, but decided to re fit oem box just to see. Couldn't really tell any difference in terms of performance just very quiet again.
Ran like this but missed the burble, despite removing rear exhaust box the car is so so quiet.
So decided to re fit filter. Pondered making a heat shield, and when re fitting cone thought I may be able to use oem box and build on it.
So took some bits off and ended up with this. A semi heat shield! Also keeps original air feed in place.
So my thoughts now are get some 4mm aluminium or abs ( any hints appreciated) and use the base of the orig box and build up, using a rubber seal at the top. Looks fairly easy. Filter will move to middle if take a little nibble out if bottom part.
Ive also found a k&n filter for a Audi 4.2v8 ( should handle enough bhp) with a 92mm neck ( normal filter have 100mm neck and are a tad big, 92mm is exact for 335d) for £45 delivered so going to swop my filter. Not sure if this makes any difference but I took objection to it being called a halfauds filter!,,
It's not, it's a simota ( no I havn't heard of them either).
So, that's the plan. Car sounds great again. I know I'm not getting massive power gains but it keeps me out of mischief!!