I've heard [censored] piped imports that almost split my eardrums with their exhaust note, and I've heard others that are much more mellow, deep but still loud (usually on cars combined with CAI's) that sound gorgeous. I assume it's the cheap Pepboys or similar 'performance' exhausts that sound the worst, a real you-get-what-you-pay-for example.
The total sum of everything I have learned from this website: ...Oil in engine, good!