Not sure a tune only will help. May take both.
2008 White G8 GT
Kooks 1 7/8 Long Tube Headers, Kooks Catted X-Pipe, Kooks Catback Exhaust with single 3" tips, SLP UDP, Volant CAI & AMSOIL filter, BMR stuff
351hp / 370tq via Dynojet (Before 2012 changes)
2012 changes - Yank Converter, DSS 1 piece Driveshaft, Forgestar F14 Staggered
AMSOIL
Initially I had some but Pat tuned that out. Really depends on if the surging and idle problems are tune related or due to your cam needing a stall. If I remember correct I thought he VMS 1.5 was stock stall friendly, maybe a little push.
2008 White G8 GT
Kooks 1 7/8 Long Tube Headers, Kooks Catted X-Pipe, Kooks Catback Exhaust with single 3" tips, SLP UDP, Volant CAI & AMSOIL filter, BMR stuff
351hp / 370tq via Dynojet (Before 2012 changes)
2012 changes - Yank Converter, DSS 1 piece Driveshaft, Forgestar F14 Staggered
AMSOIL