I am asking this question to see you guys have seen the same thing as I have. I am only referring to fuel and spark not mods. I am by far not a professional tuner nor is my buddy. He just happens to have a mobile dyno to play with. I have had the pleasure of playing with a V-Max (carbs) and ZX6 (EFI) and my results were very similar with both. With the V-Max, I ran the A/F from 8 all the through to 14 and only saw a max of about +- 2 hp difference. I changed from the resistor boots to non-resistor boots and there was absolutely no difference in HP. Remember this is all top end HP. BTW I can rip out carbs on a V-Max, change the jets and replace in under 20 mins now LOL. I saw the same results with the ZX6, the power between A/F was not much at all. That said, when the A/F was right, both bikes were much more crisp and my butt dyno said different than what the mobile dyno said. So my question is, I see alot of threads with a 10 hp gains just from a tune is this normal? That said, I have also personally seen false gains from an un-named bike/tuner shop. How did that happen? I took my bike there (before I met my budding on a vmax forum) and they did a base run. We met another guy that had his 2 sheets from them (claimed 11hp gain) at a spring dyno day. The dyno on my bike was within 1 hp between the 2 dynos. His dynoed out within 2 hp of his baseline. No where near an 11 hp gain.