Hmm....... don't know how cheap you're talking....possibly a performance chip?
http://shop.ebay.com/i.html?_trkparms=65%253A12%257C66%253A4%257C39%253A1%257C72%253A2464&_nkw=pontiac+g6+performance+chip&_dmpt=Motors_Car_Truck_Parts_Accessories&_trksid=p3286.c0.m14&_sop=16&_sc=1
don't know if its crap or not, but most feedback says they see results
plus look at the prices
you could always put a new muffler on to sound better
(and im not talking about to sound like a ricer)