Remus is expensive, but Borla probably is as well. Magnaflow and Flowmaster are great mufflers, but I wouldn't use them for BMW cars. I think the emissions for BMW are a little different so they might not do anything for you. BMW's already have pretty good mufflers. Magnaflow and Flowmaster work great for american cars because the stock mufflers suck. Gives them a great sound for 300 bucks.

If you just want sound, then go x or straight pipe. Cheap and fast. There are some clips on you-tube.

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Eazy wit da Haaahdwaire!!!!