hello guys, to give some back ground i just bought a 04 f150 HD with the 5.4, auto tranny and 4.10 gears. I already have the banks ram air intake and ottomind programmer. trying to figure out the best exhast setup. the truck has all the cats with just a 2.5" glasspack dumped. was wondering if a 3" system would be better for torque, thinking dynomax bullet turned out the side in front of wheel. Not looking to run duals because of the salt up here in NY. Any input is greatly appreciated.

 

a 3" single exhaust will perform better than 2.5" duals in the terms of torque, and the Bullet will sound great. Bullet's are 16 gauge aluminized though, they will rot if salt gets to them. Next best thing would be a stainless round body Magnaflow.

 

i had also thought about the round body magnaflow, would it also be worth changing the y-pipe to a magnaflow y for smooth transition

 

Round body Magnaflow mufflers sound great. A bit loud but great.

Yes, the stock Y pipe is restricted inside with cheap cuts and a 2.5" dual in to 2.5" single out design. The Magnaflow Y pipe is fully smoothed inside, and does 2.5" dual in to 3" single out. Definitely a healthier performing, and better sounding system. The best way to go for a 3" system.

 

I think that going to a 3" mid pipe will not increase your low end torque. If anything, it might hurt it a little. Your system will have greater velocity with a 2.5" mid pipe and a better y pipe. That being said, your mid to high RPM range will suffer from the 2.5" mid pipe. So, your "passing gear" power will be better with 3". Your call.

3" will sound awesome too!

 

with all four cats, will the 3inch exhaust help with low and mid range. it seems a little sluggish. we have a 2005 superduty with a 5.4 at work and it only has two cats and a stock 3inch exhaust and it seems to accelerate much smoother.

 

^ I seriously doubt it. When you enlarge that mid pipe, you are decreasing your exhaust velocity at low engine speeds. Thus, raising the torque curve to a higher rpm range. I suggest leaving the 2.5" mid pipe for max low end torque, but also consider removing your rear cats and replacing them with 2.5" pipe. This might give a little boost down low.

 

i thought about getting rid of the rear cats , i did it to a buddys fx4 with the 5.4 with only 47,000 miles and they ended up being almost plugged, i think i might pipe the cats and go with a magnapack muffler to keep the torque thanks for the input, greatly appreciated.