On my 6 speed, I deleted rear cats and placed a magnaflow 2.25 dual in / dual out and ran duals straight back, making a long sweep bends after differential instead of the sharp bends with quad tips, I like it, got ride of 90% of the drone, what I was going for.
1st time shop put the sharp bends in, instead of long sweep what we talked about, and the drone was worse, took back and got fixed how we planned and drone went away

Larger diameter pipes deeper the sound.