I have mine straight piped and i dont think its really that loud at all! just during idle while warming up between houses lol. on the road at 1500k RPM,s i cant even hear it and also the same on the HWY but at 2K RPM's

 

The sound of the flowmaster was alright but not loud enough so I put it in the shop for 2.5" true duals with 18" glasspacks.. The sound was louder but had a rice burner or strait six sound, sounded like I had two strait six's under the hood and they were exiting separately one on each side. That lasted a few days (till my Magnaflow got here).. I replaced the glass packs with a Magnaflow dual 2.5" in and dual 2.5" out.. (Magnaflow 12568 Satin Stainless Steel 2.5" Dual Oval Muffler ). The sound is a little better now with a mellow tone at idle and a good tone cruising but revving in park still has a rice burner sound above 2-2500... I'll try to get a video up in a few days..

 

No doubt, when towing a 7000 lb load, there is a decent load of drone from a 40 series. I still like mine though!