[sethchid]

Hey guys, new to the forum, and glad to be here! I have a 2005 SuperCrew FX4 with the 5.4L, K&N CAI, SI/DO flowmaster 40 series and soon to be installed Gryphon and I'm looking at getting a set of pacesetter log tube headers, magnaflow highflow cats, dynamax race bullets and an "H" pipe. The headers have a 3" collector on them so my question is this: Should I get the 3" magnaflow highflow cats and keep it 3" to the back or should I reduce down to 2.5" before or after the cats instead?

[mwood1986]

I've read in a few posts that they say 3" max so I wouldn't think it'd hurt anything.
I ran 2.5" back with an xpipe and got way more torque than true duals alone so the h-pipe should do the same for you.
If I had 3" off headers I'd personally run 3" back but that's just me. Pacesetter even carries a y-pipe you could probably retrofit into true duals also if you're hanging the exhaust yourself, I also read that the Pacesetter LT's sometimes hit the frame when you put it in reverse though also.

I haven't installed headers yet, just done lots of research for future plans to.

[jmt0645]

if you want true duals stick with no larger than 2.5" tubing, dual 3" will kill your bottom end power curve which is where these trucks need as much power as possible. FWIW i've been running the coated pacesetters with y pipe over a year and a half and love it. but i've never heard about them hitting the frame in reverse

[mwood1986]

He had the black painted ones on a 4x2 but yea could be a factory defect as well, I heard it's a bit tighter on a 2wd. If the 3" with an H pipe is too much flow then I'd think he'd be fine with an X pipe or just go 2.5" it's all up to you and I know you lose a lot of nice sound with y-pipes.

I was looking at this for when I go to redo my own exhaust:

OBX HEADER EXHAUST MANIFOLD 04-08 FORD F150 F-150 4WD | eBay

$570 and it's all ss I was just going to get someone to tig an x-pipe on it. Seen a few good responses on them also.

I think it's $170 more for cats instead of resonators or get a custom tune it's a bit more but, it'll never rust.

OBX HEADER CAT'D 04-08 F150 F-150 5.4L 4WD 4X4 Manifold

[88Racing]

Stick with 2.5" pipe....this will help maintain the lower part of the torque curve....

[hampsterzone]

I have Edlebrock shorty heaters, stock cats, stock piping from cats back, dual exhaust, 3" pipe from midway to tips which are 5" echo tips. Sounds mean! I do not know about loss of low end torque though. But I have 4.56 gears so I am not sure I even noticed. ? (straight piped)

[DarrenWS6]

3" true duals on a N/A 3v engine and stock size gears are going to kill the transmission and strain the engine down low. Don't do it. 2.5" at maximum. And X piped. Start the 2.5" after collectors, before the cats.

Here is how hi-flow cats, 2.5" true duals X piped with Dynomax Bullets and 4"x18" 45'd tips sounds.

http://www.youtube.com/watch?v=Vi-L12mt5E4