[matty69b8]

Has anybody used the n55 mid pipes to delete the secondary cats on there n54 335i I'm really wondering if it will still pass a uk mot?ie visual side of things?
I still have my oem downpipes on the car but would just like a bit more sound I know a few others that have done this stateside with good results.
Thanks in advance
Matt

[doughboy]

Missing secondary CATs won't pass a UK MOT on emissions let alone visual.

Primary means 'first' rather than 'most important'.

The secondary CATs are the main CATs emission wise, the primary CATs are there to heat up quickly for the 2 minute cold start emissions, which are not MOT tested.

When the exhaust is warm the secondary CATs do more work (they are much larger).

Deleting Primary CATs will give a great sound and still pass MOT

[matty69b8]

Thanks for the info doughboy looks like it may just be worth going down the catless downpipes route instead then if it will still pass an mot ok that sounds great to me more power aswell!!