[doughboy]

Yes it's the milltek OPF bypass with sec Cats. They did the same product for pre OPF M3/4. You can buy it with or without 200 cell CATS. It's aimed at those wanting primary cat delete but keep MOT pass.

So now the car is the same as a NON EU car with milltek mid and back boxes. But better in that the new sec CATS are high flow versions.

My theory is the slight back pressure from the SEC cats might keep OPF sensors happy as that is all they monitor, which after 150+ miles it seems to be working, but time will tell.

If I went pure OPF bypass then it would be too noisy with prim CAT delete later on, and fail MOT emissions in future, which does concern me as I intend to keep this car a while.

From my N54 days it seem's even OE secondary CATS have very little effect on performance, it's the primary CATS that have the most effect.