You will usually pick up a decent amount of power over a base map just simply because you should be able to push additional ignition timing. So even at the same boost you can generally pick up ~20whp. The important thing for companies that are including tunes with their kits is reliability. What that means is that ignition timing will be dialed back from the jagged edge of detonation. These motors are relatively det prone as it is which is why its important to have a good knock free tune.
Either way no matter how good you feel like its running on the tune thats included with whatever kit you get, get it verified with atleast 3 power pulls on a dyno.
Thanks,
Alex Goodwin
AlexG@motionlabtuning.com