Alright I've been asked for this a while so figure Id make a thread to help anyone out.
I have a 550i (N63) and I bought on eBay the Megan Mufflers with the 2.5 piping for the 535i. The 550i has 2.75 stock piping, but lots of kinks thru out, so honestly I didn't care. I've had the mufflers on for about 10 months now and still love them.
I have a M5 CF diffuser installed and the mufflers were adapted to it via custom hangers, it was an easy task for the shop owner. They sound great and deep, slight drone around 80mph but honestly you tune it out quickly with music or forgetting about it. I don't notice it anymore, I just remember from when I first installed it.
As for performance wise, It felt a bit quicker ? but nothing crazy. I love you can hear the turbos a tiny bit better, with Down pipes it'll sound great, Id love to get them but not in my budget at the moment.
I took a personal video but I don't think it really does it much justice, I did however find a 650i (n63) with the Megan mufflers as well and the sound is a bit more real life.
