I have RotoFab, Cortex, Solos, and otherwise stock exhaust. I do get a little drone between 55 and 60 mph, in 6th gear, other than that, they're great. The key is turning off DOD. I test drove a G8 that was totally stock except for Solo Axlebacks, and really didn't like the noise from the 4-cyl mode. It wasn't so much a drone, as it was a vibration. Would quickly get annoying.
2009 PBM GT
Under the Knife Again
Wiseco Pistons, K1 Rods, Johnson Lifters, BLP Keep Hatin' PDS Cam, Roto-Fab, BLP Ported Intake and Throttle Body, Kooks 1-7/8 long tubes, XForce Varex Catback, ZL1 Converter, Camaro Trans Pan/Filter, GXP Brembos
Breyton GTS-AV Wheels, 6k HIDs, Holden Steering Wheel and Paddle Shifters, Eibach Springs, 35% Tint
Tuned by Day Tuning