When I bought my stock 325i, it had a Cowley back box. Wasn't very loud but had a decent straight six noise mid to high rpm. Was a long time ago so I don't Know the dimensions of that particular box. Was an oval box tho, if that helps
Get an e36 m3 exhaust and put a branch... you will be amazed at the sound.... but that's only if you can still find one.... else try TNT in Germiston... check out their price on the branch you will be surprised... maybe ask them about full systems as well..
I have a great condition stainless steel single 63mm freeflow system using 3 wildcat boxes that I just removed off my e36 328i. You welcome to purchase it from me, I will even fit it for you. It sounds great and there is zero drone.
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