what kind of gains do you get when installing a cat back exhaust system like magnaflow flowmaster or otherbrands

 

Nothing. Until you get rid of that restrictive Y-pipe, you're gaining a grand total of nothing.

 

Sound, and that is about it.

 

Even with the stock Y, I believe you'll gain a little as the Y is not the most restrictive portion of the stock system. The stock muffler is. A cat back with two TPs won't hurt.

Not sure if there are any charts on cat backs vs stock, but I know there are independent test of mufflers on the net.

Will the gain be enough to notice? I don't know that you'll feel it much but it'll have a little sound. You might notice it in actual gas mileage over a regular route, maybe not, certainly no worse.

If it just makes you feel better driving the truck .... that has value. Even if I didn't think it added a single HP, I'ld have at least added a cat back with the twin tips for the looks and I like a little tone on my triucks (though I did add an extra muffler to kill droning).

Bang for buck, a tuner gives more.

 

Not trying to argue with anyone but I just recently installed a Magniflow SI/DO cat-back and did the air intake snorkel mod and it was a noticeable difference. This is on a 2006 KR F-150 4dr, 5.4 4x4. Prior to these mods I was averaging 13.8 mpg in town, now I'm getting 15.2 mpg. I haven't had it on a road trip yet so I'm not sure what the hwy mpg is. I am going to buy a tuner real soon, also considering OBX long tube headers and that is why I haven't bought the tuner just yet.

 

just minor economy improvements since a cat-back ) good quality stainless flow through one ) eliminates restriction and allows for low velocity.

Headers and a tune with hi-flow cats adds up to a very well performing system.

 

well since it is going to be a cat-back you will keep the stock y pipe that connects both manis which kills your flow! You will gain a little something, nothing thats going to make you think your truck is way faster though... I think its a great idea man, enjoy the **** out of your ford. I just cut my muffler off and welded a 2.5-3 inch side exit straightpipe!