uhm.. the more you mod, the more your car becomes different then someone elses. That should be fairly obvious.
The reason they make maps less aggressive than they could be is because they have to fit correctly on EVERY car. Lets say the average car knocks at a timing level of 14 at 16.5 lbs of boost at 3500 rpm (mine does, but im on 91 :P). Your particular car may be able to do 16, but there are cars who will knock at 12. They have to shoot for the "best fit" and will use a level low enough that almost every car will run without det'ing.
If you want more power you'll have to get a custom tune. No way around it.