I drive a 99 F-150 4x4 5.4L. I currently have a Flowpro power pack s/i d/o out the corners into four inch magnaflow tips. I wanted to switch to 2 1/4 inch true duals off of stock cats into H pipe with two Flowmaster original 40's. Would I lose any bottom end torque with this true dual setup?

 

Yes

 

Don't know any actual stats but, I'm going to sound like a broken record (if you've read before please disregard), I did 2.5" cat-back, Magnaflow X-Pipe, & 2-Dynomax glasspacks exiting w/ dumps just behind cab. The performance is QUITE NOTICEABLE!! Granted I'm running a 4.6L, but should be close.? These true duals sound, look, & perform gr8. Good luck on what you come up w/!!

 

No.

 

I lost low end torque with one si/do flowmaster..

 

Yes you will lose torque with the Flowmasters. Run two Magnaflows, or the Magnaflow DI/DO with the built-in X-pipe and that should work well!

 

What size maggie will work in the DI/DO configuration and what's the part number?

 

11386 is the part# for magnaflows 14" DI/DO with thru-X. Bought mine off ebay for $75 bucks free shipping. About $50 bucks cheaper than anyone around my local sells 'em for
Just bought the muffler and 2 18" SS tips for mine. Waiting to put new wheels, tires and body lift on before I have 'em installed though

 

How loud are the magnaflows compared to a 40 series flowmaster?

 

I went true duals with 2 40 series and the truck sounds and performs great. I have not noticed and low end loss rather a nice gain..i say yes

 

You wont lose any low end as long as you put an x pipe in and use 2.25 pipe. I have no cats, true duals, x pipe, 2 magnaflow 14" mufflers with 2.25 pipe into 3.5 tips and I noticed a very nice power gain from my cat back I had before. You can probably even use 2.5 pipe, but I wouldn't go over that.

 

Go with Magnaflows.

 

Hello 99fordman,

I have a 2000 5.4 4x4 (same as 99) with Magnaflow SI/SO and I definitely have more HP and Torque, I herd bad things about losing low-end with SI/DO so I stayed away from it.

 

I found this muffler on ebay for 86$ obo. Casper, was yours brand new when you got it? Also, if I got one of these mufflers, it says it has the tru x built into the muffler. With that being said, I'm assuming that I won't have to buy an external "x" pipe to place before the muffler? Thanks for your help!

 

NO