So, the 2002 R50 is in the shop. Chief complaint was a sound that I equated to a roar. It would happen when accelerating, as if the engine was straining to achieve its RPM. I changed out the plugs to NGK OEMs and the problem had stopped. It then came back. I had a concurrent "service engine soon" light corresponding to burning lean.

The dealership told me the air intake boot was cracked and they replaced it. They told me the light went out (hopefully permanently). However, they told me the growl was still present. At a subsequent conversation, they told me it was more of a whistle, so I think they are talking about another sound that could perhaps be attributed to the passenger side window not being full up. In other words, I haven't picked up the vehicle and don't know what to expect...

So, from what I've described, do you believe that the air intake boot was definitely responsible for both the SES light AND the growl. It's actually the latter I'm concerned about since I don't need my car inspected until 9/2017, by which point I think the MINI will be gone. The growl is very irritating, can limit the effectiveness of my ramping up speed, and makes me wonder if the car is about to fail...

Thanks for your thoughts, enthusiasts!

P.S. My title says "(I think)" because I've been told that sound can travel in the most irregular ways, so that something which sounds as if it's in the front end can actually be coming from somewhere else. Thx!