Is there any way to lean it out a bit without power commander?...aftermarket cans?...K&N filter?...i dont want to put a pc on it if i dont have to...
You don't HAVE TO do anything, if you're happy with the way it is.
BUT If you want it razor sharp all the way from under load as 1000 RPM through to the limiter at every map co-ordinate, can pay a PC, and will pay for a PC, then why wouldn't you get a PC?
There's a good number of members who have canned their 919s and they run fine without a PC.
K&N air filters and others like them really aren't worth debating in terms of performacne gain. I use a BMC and look at it as being a lifetime filter and nothing else but.
I had air filter comparison dyno runs done as a personal research matter.
The short story is some effect on torque stability at low revs, I mean in the 4s, but more torque at peak, and no difference at peak hp and beyond.
There is very little gain with a 919 in this regard.
My theory is that the pleated woven cotton filters do not dampen out air box pressure fluctuations as well a factory filter, which then effects what the MAP sensor sees.