Where ever you place them the velocity of having dual 3" will be terrible. 2.5" should be the maximum size to maintain velocity and is more than ample flow. Look at almost all of the supercharged members on here you will see that 2.5" duals are more than enough to keep up with forced induction. The larger pipe diameter kills scavenging even in low boost and since most trucks don't run more than 10psi the need for larger piping is not needed.

 

ok, I was thinking that since it was necked down to the Y-pipe already, that what was put on after wouldn't matter. Thanks for the input

 

I have an 05 with the 5.4...went to racepartsdirect.com and got a whole kit including flowmasters super 44 muffler SI/DO, chrome tips and all the prebent pipes for 220$ with free shipping...the kit comes as a complete bolt on kit..with the only welding needed to be done to the tips...bout the best i found for the money....i went to a local muffler shop and had the whole kit welded including the tips for 60$...so for 280$ i got everything welded up as where all the local muffler shops were wanting to charge 350-400$ doing it there way...check out the web site...it worked out well for me www.racepartsdirect.com

 

Good deal

My parts for true dualing after the headers were as such
X pipe 40 bucks
2 bullets 60 bucks
2 tips 60 bucks

Welds and piping...thats another story

 

I want to cut the muffler out and install a magnaflow using the existing factory tailpipe. Has anyone done this? Which one did you use? The tailpipe is centered but the pipe towards the cat. is off center. Is there any issues installing it because of this?