Say you have an engine.... ANY "street type" engine. Once a competant tuner tweeks the fueling and spark at each load point on a dyno (the only 2 paramaters there are), no one in the WORLD will get more power out of the tune-up.
AND NO mail order chip on the planet will make as much power as a well DYNO tuned chip for YOUR car, YOUR level of carbon build up in the chambers, YOUR altitude, YOUR gasoline, YOUR level of deterioration of your cats, YOUR ring seal, YOUR bore wear.... etc.
If you think your chip that was developed on someone elses car will make as much power as a custom dyno tuned one, you are smoking crack