Perhaps I am less tolerant (or more discriminating) than you guys (and apparently your girlfriend too). Drone was present before and after header installation, no change. Drone is gone now that the x-pipe has been removed and replaced with the stock x that has a resonator (this makes an obvious difference). Supersprint also manufactures an x-pipe for the e46 M3 -- it has a resonator. Headers do not cause a drone, rather, they add a nice raspy tone and significant hp gains, particularly w/the ESS tune. You should get some, see for yourself.
You may find the following thread informative about headers:
http://forum.e46fanatics.com/showthr...hlight=headers
Check it out.