My set up is true dual 2.5" pipes with two 40 series flowmasters and 4" tips, its got a good low rumble, but its not too loud. I wish it was louder haha. Sounds good tho

 

I drive a 07 screw w/ 6.5' bed and I just did a custom catback 2.5" true duel with slp loudmouth 2 mufflers straight out the back with 3" tips (all welded) and I couldn't be happier with the sound, it's quiet in the cab but has a deep rich tone behind the truck, really loud as well