Has anyone fitted a AFR gauge to keep an eye on  fuel air ratio on their z8 ? as mine appears to run lean I'm thinking it maybe a good way of finding out if it's lean or rich.

I use one from ejk, works great, I use just to tune in then remove

I installed this one in my previous rig. Worked great and was AMAZING for tuning the AF mix
http://www.innovatemotorsports.com/products/lc2.php

I have the LC-2 on my drag car.  It's been working flawlessly for years.  If I remember correctly it even comes with a software data logger.

For me i Check the a/r with the Power commander .
Very easy and i can ajust  it easily with the autotune.
The best result is at 13.1 on my Zforce

~13 is really the sweet spot for these types of engines from what I have seen.  I got the EJK and that is the one thing I wish it had was a AF ratio output...oh well I may just get the LC-2 again and put that on the CF Moto.