I have a Draxas header, f2 flex and nothing but a resonator the rest of the way. I LOVE the sound. The drone isn't that bad (if you ask me). The header and flex are 2 1/2 and the MBRP exhaust is 2 1/4. It took a little to get used to the sound, but now I can hardly hear it. Everyone always tells me how loud it is, but it's normal to me.
Current 2012 stock Focus
SOLD 2006 ZX3 SAP, Draxas Header, MBRP exhaust, CAI, Tuned, Debaged, FRPP lowering kit, SVT 5spoke wheels, Black Halo Projector Headlights, Niteshaded Side markers/tails, Mazda rear wiper, mustang antenna