[GreenOne]

3. 107.5 by spec. see service manual snip below. Measured 100% accurate would be somewhat engine specific. (chain stretch, tolerances etc.)
4. Although a difference in fuel requirement is expected even for a inline 4, it`s not very common for the average joe to do this because of the effort and cost vs potential gains. Probably not many people with experience here.

I can only speculate on the others, so I won`t

 

[GreenOne]

From the spec i posted above you should expect to be at 112/107.5 stock. With 110/108 you might be going in the direction of less peak hp and shifting the powerband lower from lsa tightening and intake advance.

 

[GreenOne]

According to race manual stock cam timing is 112 104 and at service manual is 112 107.5 that's why I asked what's the true (measured) cam timing in gen4.

Yeah, would have helped if you mentioned that you asked because the manuals have conflicting info. Pointing towards error in the service manual. Have you seen this post?
http://www.zx-10r.net/forum/f28/cam-timing-241010.html