You need the pipes that connect to the manifolds modified. If you are in Vic i can point you to the guy who did the HSV LS1 twin pipes to my V6. he does a great job and is around $100 for the mod's.
will a standard v6 still go ok with a duel exhaust? i was thinkin about getting extractors and a duel exhuast on mine but wasnt sure if ide have enough back pressure