I have a 99 F250 LD w/ 5.4, 3.73 gears, 4WD. I've modified my airbox and put in a K&N. I'd like to open up the exhaust, but I don't want to go overboard. I'm not looking for a nice rumble, I'm looking for more power. I had a 3" cat back w/ Flowmaster 40 on my 93 F150, and I think it helped, but not that much. I also think it was a little loud.

I was thinking of going with a 50 delta series on the 99 and staying with the stock pipe, but most of the muffler shops I've talked to (including the one that's done my last 2 trucks) have advised my to go with the 3" cat back with the 5.4. Will the 3" really give me any more power, or will it just diminish my low-end torque?

 

C'mon, I know some of you must have an opinion on this.......

 

All the cat-backs that I've seen bolt on at the first joint behind the factory Y-Pipe. The factory Y-pipe has 1)2.5" exit. A larger pipe or dual out muffler behind this does nothing more than what feeds it; 1)2.5" pipe. If you like FM, they provide sound graphs for all of their mufflers at their website. Your FM/DF50 w/stock pipe sounds like a nice improvement.

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2000 F-150 XL, RC, LB, 5.4L, 4R70W, 3.55LS,
Class III tow, Payload #3, & Convenience pkgs.,
4-wheel disc/ABS, Chestnut/Parchment 40/60,
Ford bedliner w/Paintsaver & gas/wheel/spare locks,
K&N F.I.P.K. w/Outwears pre-filter, Superchip,
Dynomax ultra-flow welded 3" cat-back w/ 3" Y-pipe,
Hellwig front & rear anti-sway bars, Rancho RS 9000s,
Mobil 1, K&N oil filter.

 

WarrenC,
I had the flowmaster 40 si/so with stock pipes on mine but wife finally pushed the noise concern on me.
Same shop just installed a FM delta 50 si/do
with 3" in and 2.5" out with pipes out the back and its a great improvement. Its quieter inside and outside still has a grumble getting on it but is easier on the neighbors ears at 4:30am.
This has all been done with the factory exhaust cut right behind the balancer(black can object) on the exhaust. Muffler guy did not recommend cutting behind the cats and running true duals for mods and driving habits. Using the si/do he claimed wouldn`t relieve the back pressure so much as to kill low end power. He has been doing it for 20 yrs so I went with his advice. I have not noticed any power loss going si/so to si/do on the truck.

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2000 F150 SC, XLT, Bright Red/Silver 4x2,Auto, 5.4, 3.55LS,CD, sliding rear window, Tow package,Captains chairs,Remote Entry, Ford Bedliner, molded splash guards,Stainless step bars and bed rails.
FM40 single in/Single out the side.Clear Corners just installed.Pretty much stock now but waiting for performance mods to include FIPK,,Superchip, new wheels/tires and new audio.