X5 05 3.0L Diesel - Removing the mufflers for stainless tips

[mbk]

Hi, I was thinking about removing the rear mufflers on my car and changing the exhaust up so that I had twin stainless tips coming out the bumper, and a section of the exhaust also stainless. I've heard that this may cause back pressure issues and may need remapping?.. I've also heard that it won't?.. If so what's involved in remapping and where would u get that done? (and rough price as I've found BMW are ridiculous if u were to get them to do anything.. $690 for a new key.. forget about it) I'm leaning towards leaving it standard now if it's gonna cause issues.. also questioning if I'll like the sound :/ haha.. but love tinkering with my car so I can't help but find myself looking for things to do. Maybe save the cash for some drilled and slotted rotors as that's definately gonna happen.