what type of bolt-ons can I install on my 05 GTO to get more rear wheel horsepower  

Hey there.

I would start with the basics..

Exhaust- headers and performance catalyticc converters are great but at least a nice, free flowing cat back sytem.

Cold air intake- Bolts on easy, impressive HP gains for the money.

Underdrive pullies- probably the most overlooked option, but a bargain.

Performance Chip- I have always had great results from Hypertech and their power-programmer line is awesome.

Rear gears- a lot of folks dont ever look at the gearing of the rear-end, and it isn't going to give you more HP, but it will accelerate faster and feel like a lot more power if you gear it down.


Hope this helps,


John  

I agree, with john,

Your definately going to want it to breath better.  Volant or K&N intake kits are the way to go.  You wanna stay away from a metal intake tube due to the heat soak issues with the 05's.

Next get a set of headers, shorty's are the easiest to install, but the gains are not as impressive as long tubes.  Kooks, or Stainless Works are probably the most popular, and if you have a budget, Pacesetters coated are a viable option as well.  

There are numerous exhuasts on the market and its all what you want to spend, and what kind of sound you want.   After that, get the car dyno tuned, sure hypertech, and predator will get you gains, but a wideband dyno tune will free up anywhere from 20 - 30 HP alone.  Once all that is said and done, you should be sitting about 375-380 HP..  Throw in a medium sized cam, and be upwards of 440 HP... with the Stock 243 Heads...

Probably looking at 3500-4000K total..

--Scott  

Great information here.

Yes, you will want to start out with bolt-ons. There are plenty of cat-backs out there to choose from, so find the one that sounds and looks the best to you.

While the Hypertech Power-Programmer can increase power, I would strongly suggest you look into a custom tune if you go further than bolt-ons. Gen III and IV cars will benefit from this sort of programming greater than a handheld programmer. The handheld units don't offer enough control for people who are seriously modifying.