Thanks for your response and it's good to know what others tried and worked for them.
I am keen to see the sound of milltek exhaust but couldn't find anything on their site. What is the price they are going to charge? Is it only single tailpipe or they offering dual/quad tail as well?
Which specific racechip product are you using ? Does it void BMW warranty ? Does it come with warranty? Those are important to me.
I will keep the filter in mind
what does it require to replace the OEM filter with the one you mentioned ?