I've noticed the last few times I've driven my Challenger that used to drone, that it has stopped.
Nothing has changed in the TTi 2.5 x pipe exhaust system. I'm glad the drone was annoying.

Take care,
Rick
68 Coronet R/T 440 & 68 Charger 528 Hemi,and 5 Challengers! 6 cyl, 318, 360, 383, 451