S/steel exaust

Hey,

I own a bmw 1 seriese 118D and want to make it sound more "grunty"
I was planning on makeing a straight trough stainless exaust but have been told I will get faults lights come up, is this true ?
If so can you guys recomend any aftermarket exausts that won't upset the ECU.

Thanks

All you need do to make it any louder and grungy is remove the cat you shouldn't see any warning lights