Pontiac GTO 2004-2006 - horsepower/mpg with new mods on my 04 gto a4??

I'm bout to buy a few things for the goat. I'm keeping it simple and not making this thing into a race car like I have with my past LS powered vehicles. It's my first automatic ls1, and im curious as to how the foloowing mods will effect my MPG, and also how much power at the crank and at the wheels you think ill be sitting at?

-CORSA catback (for an 04 bumper)
-k&n Cali
-slp underdrive pulley
-Diablo predator (preloaded 93 octane tune)

That's all I'm doing to it. I just wanna know do you think my MPG is gonna go to shit? Or barely be affected in a positive or negative way?? And of course what's the HP you think it'll make based on your own exoeriences

That's CAI. Damn autocorrect

that is what i have done to my 06. Mine is an automatic and I get 16 mpg around town with it and i hit 20 mpg on the highway. Not to sure about the horsepower but the tuners give about 20-25 horsepower.

thats not bad at all. Anyone else? 63 people and one responds.

18 to 20...

I'd almost do a trans cooler too, for piece of mind.

You can probably get some low 20s on the highway, if you get a real tune and enable lean cruise you can bump that up to the mid 20s.

Not trying to thread jack , but how do you enable the lean cruise? I'm trying to get my 04 done?

It's a parameter in the PCM that you can enable with a tuner software such as HPT or EFI Live. I don't think a handheld can do that unless you have someone with access to the backend of the software enable it for you and then send you an updated tune for your handheld.

For the price I'd find a friend or two to go in with to buy Hptuners.....you can do SO much more and get a lot more features end all for $650.

With a 3,000 stall and exhaust only on mine I was getting about 18 city and 22 highway after playing with lean cruise and fuel decell

My tuner has efi live. I'm trying to tell him the parameters to look for, so any specific section ?he doesn't usually worry about mpgs lol

For the OP. It looks like for the $1,500-$2,000 you'll be spending you won't pick up hardly squat for power. Catback= 5 HP . K&N=5-10 if you keep the hood open, UD=5 and a handheld gives a crappy limited tune. Get some good LTs and a real tune and you'll pick up 25-30 RWHP. As said lean cruise can pick up 10-12% better highway mileage.

For the person asking which parameters I don't know exactly where they are in EFI as I have HPT. With that off the top of my head you adjust under a "lean Cruise" tab where and how much it leans by MAP and RPM, lean out rate, what speeds it enables and disables, delays and timing modifiers.

Yeah your right svede. I'll put the Diablo money towards a dyno tune and ill eventually get some longtubes.. just not right away

The best thing about LTs are they do a lot of different things. You gain power, sound and they support any other future mods you do.

I'd almost do a trans cooler too, for piece of mind.

Absolutely no need for what he's doing.

....but +1 for everything svede told him.