For Tracy,

 When I was actively tuning race cars we had a truism that I often used, "everything changes everything". This was a drastic oversimplification, but none the less was true. If you have an engine running very well, a seemingly minor change WILL change exhaust note or timber. On the dyno you would find some adjustments did little, others a great deal. The fact is as you get the mixture closer to right I am afraid you will hear the exhaust not come back up in volume.

Bill Jepson