"Thank you for the much thought out response. So, essentially, in my situation the only thing I can do is swap out my GHL for a properly designed, non resonance exhaust (i.e. CarGraphic, FabSpeed, Gembella, etc)?"
I would be careful with which of the exhausts you choose. I have headers and 100-cell cats, and I found that the Gemballa muffler and the sausage-style Dansk muffler both give that 2-3K resonance that drove me nuts.
I finally settled on a Dansk OME-style "sport" muffler, which has higher flow rates than the stock muffler. It is only slightly louder than the stock muffler and has no resonance issues.
BTW, the "butt dyno" seems to registrar a difference with the higher flow rate with this latest Dansk muffler. With the stock muffler the car would make a noticable increase in performace at 5.5K. Now, it pulls strongly from 4-6.5K without that transitional jump at 5.5K, something is going on.....
Ed
