If I were you I’d skip the 18 and get the 5x11x22 Magnaflow PN# 12588. It’s the same muffler used in the magnaflow catback. When you delete the resonators it sounds fantastic! There is zero
drone in the cab and the exterior sound is pure motor music. That’s what I’m running.
A buddy of mine has the 14” Magnaflow with his resonators still in place and I don’t love it.
In a direct comparison the 14 is louder, both inside the truck and out. However my 22’s exhaust tone with the resonators deleted sounds deeper. The 14 drones to the point of annoyance, where as you have to listen to hear my 22 inch muffler while driving. When you step on it… both trucks scream.
I think the lack of drone has to do with the 22 having a larger case size, it's a 5x11 instead of a 4x9.
Remember sound is subjective but I thought I’d give you another option just to complicate things