So a few months back, whilst I had been waiting patiently for Remus and Akrapovic to release their M340i specific exhaust systems, I decided to swap out the factory downpipe for a 200cpi high-flow DP from Evolution Racewerks in an effort to add a bit more excitement and presence to the stock/factory exhaust note. I'll be tuning the engine shortly too, so I wanted to reduce turbine housing backpressure before turning the wick up a bit on the B58.
I'm very pleased to say that cold start even in Comfort mode is a bit more entertaining (lol), more importantly the exhaust note overall in Sport/Sport+ mode is much improved. In particular partial throttle burbles are more dramatic, WOT shifts have more of a bark and down shift throttle blips are definitely more satisfying.
Having recorded a video standing behind the car I couldn't really detect any nasty smell once the cat is warmed up. I've only had the one CEL so far relating to poor catalytic converter efficiency (lol) and that was easily cleared via the MHD Tuning App.
All in all I would say a high-flow catted DP upgrade is a relatively cost effective way to increase the aural pleasure of the M340i stock exhaust note, without the drawbacks of going to a catless DP.
Of course a post discussing Evolution Racewerks products, in particular their fancy looking (haha) and beautifully fabricated downpipes wouldn't be complete without some pretty pictures.
Lastly I have several of these M340i ER catted downpipes in stock and I should note that for F-Series B58 owners they are also direct fitment.
Cheers,
Justin@JDTuning.
https://www.facebook.com/JDTBMWPS
Ph. 0421 641 381