I am running flowmaster 40 3"in 3" out, side out before tire. i was running magnaflow super 40 did not like.

 

There is a big difference between chambered mufflers(ex. Flowmaster's) and straight through mufflers(ex. Magnaflow's). Magnaflows sound more tuned and cleaner but have a nice mellow rumble. Flowmasters dont sound as clean as a Magnaflow but they can make you truck sound like a bigblock if you get the right series, I know it made my '05 Stang GT sound BaddA$$ and loud with some minor resonance. The magnaflows are not the type of muffler that gets louder the more you get on the gas, instead they just seem to sound better at idle and low Rpms and quiet down the higher the rpms get. I like both...good luck!!

 

i welded a glasspack resonator in place of my stock muffler...$60 and sounds great

 

I bought 2 magnaflow mufflers, and then took it to my freind who owns his own shop. We cutout the area at the Y and ran true duals on my 05 Fx4
Also did this on my 01 XLT. Sounds awesome and with a closed cold air intake and custom tune sure woke this truck up. Here is the Mufflers I purchased they were not cheap but well worth it, I did this in April 05 about a month after I got this truck.

http://www.magnaflow.com/02product/s...ne=main&id=484

 

My muffler guy said that if the Magnaflow SIDO was a bit too loud for me, he could stick in a resonator to tone it down a bit more. Didnt do it, gotta keep the exhaust noise up with the air intake noise. (I think my gas mileage went down after these add-ons) Foot got heavier.

 

Definately leaning towards the Magnaflow..