I am building my 2006 GTO into a drag car in a few months.

first off how much power are you looking to get? The best way to find out RWHP is to put it on a dyno before your build and dyno after your build. There you will see the gains. Will you be doing any suspension or gear swap? If I had to guess with your mods, maybe 45-460 RWHP

with the right port polish job u can get a solid 40hp, another 40 with a good cam, long tube headers 15-20, cat-back exhaust another 15, cold air intake 10-15....keep in mind price on the port polish job, u can get new heads for a few hundred more and get more hp

Call Ed at Flowtech Induction. He will do the best port job on your heads that can be done. He will also pair a custom grind cam with your goals and head work. If you don't go this route you are most likely wasting money. The only other place I can think of that is comparable is Advanced Induction. Headers: go with Kooks. But you are missing the biggest weak point of an LS2....the intake. it sucks. You need a Fast 102 otherwise you will be losing a ton of power. Intake: Duspeed or Svede OTRCAI are the best. Period. Vararam is ok. If you buy a different intake or make a custom intake you are completely wasting your time unless its an "over the radiator style". This has been tested extensively. After making all this extra HP you better contact G-Force as well for their anti-hop rear axles otherwise your car won't move off the line for crap. You'll also find the stock suspension is completely trash. Contact Andy at Kollar Racing for help. Lovells and Whiteline products are sold there. Otherwise there is Pedders from Wretched Motorsports but its a bit more costly and not really any better.

Oh and for a HP mark....450+ at the wheels with what i suggested.