Exhaust question..

[Nuttzzy]

So guys i already been threw the HID phase and all that now I'm looking at performance.. have about 1k to spend or so.. so i was looking at a CAI and Bear.. question about the exhaust.. now on my past cars.. (2007 Cobalt SS/SC and 2010 MS3) it wasn't necessary to change the exhaust until a certain amount of HP or engine performance.. there was just no plus in changing it because the restriction of the exhaust wasn't enough to reduce power and the stock or slightly modded stage.. now I'm not looking for a track or racing rod.. just a little more get up and maybe some milage out of the 5.3 Vortec.. so i guess my question is, is the stock exhaust efficient enough to deal with a CIA and tune? or should i just change that out and be done with it? wasn't o keep it as close to stock sound as possible maybe a low end growl but no straight pipe roars.. have the 2011 LTZ with the 5.3 Votrec has the E85 option and 4/8 economy thing... thanks for any input