Crash, is your Magnaflow a single in dual out or a single in single out muffler? I have a Flowmaster single in dual out on my 03 5.4. I doubt I will switch but will maybe try Magnaflow on my next truck. People have been saying that they provide a better performance gain. I did not document before and after I got my Flowmaster, so I dont know if there was a gain or not. I have an interior vibration in the cab as you described but it is only at start up when I am backing out of my garage.

 

Both systems are/where Single In Duel Out (SIDO). My issue with the vibration so everyone knows is they mounted the Flowmaster by welding the mounts to the frame. This is very wrong and especailly noticable on the 2004 and up trucks. Because the frame on these trucks is so stiff, any vibration addition (in my case the Flowmaster drone) causes vibrations in the truck. It is most noticable when the Flowmaster starts to rumble. i.e. when you step on the gas or get up to highway speed (45mph and up)

He proved it to me by telling me to down shift. e.g. higher RPM's and the Flowmaster Rumble

The Flowmaster definately sounded the best IMHO. But the performance difference in the Magnaflow and the fact that it sounds VERY GOOD was a huge selling point for me. I didn't know any better when I purchased my truck (Oct 2003). Since it was dealer installed, I knew nothing else.

I do know the difference now and would recommend the Magnaflow to anyone!!

Heres a Magazine article that helped me make the decision:
http://www.magnaflow.com/05news/maga...reettrucks.asp

This is for the 2004 and up F150's....