I have a 03 5.4 with cold air intake and custom exhaust with trual duals x pipe and first set of cats taken off will shorty headers add power

 

No - Long tube headers might though.

- Jack

 

Combined with a tune from a reputable tuning house.

 

The oem intake is a cold air intake, so there is no hp/tq gain. Duels/X-pipe, maybe 5 hp at the rear wheels. Cat removal, none....here's why, the cats are high flows from the oem and when dyno tested on a 500 hp SB chevy, there was no loss of hp with or without cats. Shorty header... well, shorties do work (gain a bit) up to about 5000 rpm then start tapering off, at 5500 rpm, that's about all they are good for which for most street engines and our engines, that is more than enough... but the gains are typically in the 10-15 hp range but the tq comes up a bit more.

 

all that will do is add some noise to impress the ricers and peg out the SOP meter...

 

It will only make you think about that it does, and get you pulled over.

 

Maybe not uuuuuge gains, but i have noticed a distinct difference - especially in the mid-range! Take a look at my post "My experience installing Headers" , I know, I should've done a dyno test before and after so there was "proof". But I really don't care (and wasn't gonna blow $2-300) just for "I told ya so" rights. Was it like "Holy shiz Batman, that's some horsepower" ! No, but a noticeable difference! More than when I did the cold air, or the cat back performance muffler single 31/2 set-up. Maybe the headers just took advantage of the few mods that I've done. Do I think it's worth it, Yeah. But,It was a bigger hassle than I thought it'd be1 Oh, and the wife did notice the slightly louder sound of the headers, If cost is no object (since u already have true duals), buy the headers that fit the best and best access to the nuts/bolts. But then, u won't know which ones those are 'till ya buy and try to install them