the first performance thing you should ever do is headers... end of story... not that it always happens, but it's the #1 rule of hotrodding, gotta make em breath.. it's not "eeking" more power from em....
a pair of long tubes, in the end, once other parts have been added gives you more hp/torque than anything else.. excluding nitrous, blowers turbos...
stock is fine sometimes, as in this case, but I generally prefer performance aftermarket parts.. BUT, I'm also the type not to buy $100 summit POS headers...
the K5 will have headers.. but I'm also willing to spend 5, $600 on em..