Honestly, you'll never know for sure with a "butt dyno". The gains are too small to notice without putting on a real dyno.
That being said, a pc5 or dobeck gen 4 will tell you where your air/fuel ratio is and that information will tell you if your losing power or not.
That being said, a pc5 or dobeck gen 4 will tell you where your air/fuel ratio is and that information will tell you if your losing power or not.