Not if you read between the lines. What I am a proponent of is running them as lean as you can versus as rich as you can. There is a lot of hp free for the taking between the two setups. The way my bike was set up, it ran fine with 155's in it but it ran WAY better with 130's. I have seen the same thing play out at shop dyno days time after time on all sorts of bikes. Like I have always warned about, most of it has to do with port velocity. Higher velocity, smaller jets. Whether or not your bike is a big port of a small port makes a big diff. So does the airbox setup. The airbox setup really effects just off idle jetting. Now that I raised my compression from 8.5:1 to a guestimated 10.0:1, put bigger intake valves in, and really hogged out my ports, I might see bigger mains in my future. I have got to tune on my new setup some yet. Airbox setups that use to just kill my midrange now barely effect it. I am going to test freer flowing airbox setups and exhuast and see what happens. Even if I end up running 170 mains with my new set up, I bet it would sound just as good minus three or four (or five!) hp with 190's in it. Typically speaking, that is the nature of jetting. THAT is what I am a proponent of!