LSA or Duration to fine tune glasspacks??

Well, back in the day, I had a set of glasspaks on my stock 361 big block. They sounded like mmmmm mmmmm mmmmm.
I rebuilt the engine and changed to a DP4B aluminum intake, AVS carb, and a 484 Purple cam. I did switch the exhaust manifolds to headers and kept the glasspaks. The sound was now buhwumpa buhwumpa buwumpa and when I went through the gears the sound was a deafening deep WAAAAAAAA!
So my guess is that it was the duration.