Serious increase in performance of petrol engines

Are there reputable companies that offer an increase in performance for GTAs?? With serious I mean, that the whole with dynamometer is e.g. verifiable. Does anyone have any idea what technical possibilities there are?? Or maybe someone already has personal experience with this? Incidentally, it is clear to me that an increase in petrol is difficult. And a new engine should not be because of the costs. Thanks for the information!!