Gotta 05 5.4L with a siso (2.5 in / 3.0 out) Flow 40. Sounds great and did not notice any performance inc or dec. Was thinking of adding another Flow 40 siso (2 mufflers) and going cat back on both. Do you think it would improve any performance and would it be a lot louder or a bit louder. Thanks

 

a search would say "NO"...go with Magnaflow for performance, and flowmaster to sound like you have performance...

 

It is my understanding that these engines need some backpressure or you lose lowend torque. So, your SISO may actually be better for performance. I have a SIDO 40 and love the sound, but it did feel like it lost a little lowend power.

 

when ordering a FM single in single out the 40's only comes with center in offset out , it's too wet to look under the truck will this work? also am I right in saying 2.5" in 2.5" out?

 

yes, stock is 2.5"

 

will true duals sound any diff or noticeably better then SIDO onthe 40 series

 

Well mine w/ 2 40s is pretty loud and throaty.I think it did lose some low end torque though.Love the sound but i will prob change it the loudest 2 magnaflows i can find.

 

kevin24,

do you have any idea what the loudest magnaflow's are. I wanted to get a flowmaster 40 series because it seems like they are the loudest and best "sounding" on F150's. but i know magnaflow has the best performance. i just have no idea which magnaflow set up is the loudest.

 

u know whos got a bad *ss sounding truck.. is josiah's.. watch his offroad video.. in the beginnning on that hill climb.. and one of the times that he comes out of that river goin up that bank.. (at the end i think.).. he hits the gas and its sound soooooo nasty!!!.. i love it..

i think hes got mag tho.. im not sure.. but if i could achieve a sound.. it would be his..

 

I am not sure yet but i will try to find out.Like i said i love the sound of my flows but i also want to get more low end power instead of loosing.I will say my truck runs verry strong on top end though.I have also heard spintech mufflers sound good.That is what built54 is running.

Rochester, NY I used to live 30 miles north of Watertown

 

OK, it seems that for say the 04 to 07 trucks that they run better power with a single muffler to create more back pressure...YES or NO? Also it seems that by going CAT back to SIDO is the best way to improve power and sound....YES or NO? It also seems that the Flowmaster original 40 can steal some of the lower end torque and HP, AND Magnaflow will increase low end torque and HP....YES or NO? Thinking now that Magnaflow could be the best way to go using a cat back SIDO approach? BIG question is if one loves the sound of the Original Flowmaster 40s...What Magnaflow muffler (Part #) should one buy to obtain the same sound as the Flowmaster 40, and is there such a thing in Magnaflow? What do you think?

 

Single muffler - not sure.
sido improves power & sound - yes.
loss with Flows - yes.
gains with Mag - yes. (+14hp & 23tq for the 04+ trucks).
Mag the best - yes.
sound - Mag sound different than Flows. The Mag is deeper, lower. Better IMO. No drone with Mag. I got better throttle response, and almost 1.5 MPG with my sido.