When you get the cam installed they'll tune the car for that intake, obviously, but yeah, depending on how aggressive your cam is you'll definitely be leaving power behind. You should be able to find a used varraram or rotofab on the site. I know I'm going to be selling both of mine here in a couple days.
2009 G8 GT
Roto-fab CAI, Kooks LTH & Catless xpipe, CTSV wheels/tires, Hawk Brake Pads, PatG Cam, Forged Pistons & Rods
G8 GT K & N CAI, Pypes headers, Solo HFC's,Solo axle backs, Custom tune, FE3 Struts & Shocks, White line bushings & bearings, Rear Cradle inserts, Moog end links.Little lunati cam 219/223 .625/.625 DOD with LS3 valves , LS7 lifters, BTR SKOO1 springs, 7.425 Comp cam pushrods & SLP UDP. AC tensioner upgrade.
V6 Spectre CAI, Overkill tune,FE3 Struts & Shocks, White line bushings & bearings, BMR Rear Cradle inserts, Moog end links
Just do some research on this site, you will find what you need to do. There is over 7 yrs of information here someone has done what your asking about.
515 rwhp - 416 Stroker - 2015
2009 G8 GT PSP, 6.8L Stroker 416ci,CM 228/234 .629/.629 LSA112 +2 Cam,PRC LS3 255CC CNC Heads,Trunion Rocker Upgrade,RCR Intake,FTI Stall 3600-3800,Trans Cooler,B&M flex plate,3.27 Diff LSD,UDP,1 7/8 OBXR LT SS Headers/SS, 3",Borla Mufflers,VCM OTR CAI,LS7 MAF 100mm,Patrick G. ECM/TCM Tune,Koni Shocks/Struts Yellow,Eibach Pro Kit Springs,LCA's w/Whiteline bushings,BMR Sub Frame Connectors,Spohn Tunnel Brace,BMR Fr/Rr Sway Bars,Suspension/Diff Bushings,PMT Rear Trailing Arms/Toe Links,Brembo's Front Brakes,Russell Street Legal Brake Line Braided SS,V8 6.0 Side Badges,GXP Diffuser,G8 Door Sill Plate,Red Shift Knob,SS Rim's,BFGoodrich g-force 255/35/20-285/35/20