whats a good range for the air fuel ratio
 

What is an acceptable range for the air fuel ratio?

I assume your talking at WOT? What is the engine set up and what type of fuel?

Frans96ss - yes I mean at WOT. Stock bottom end with the following:
cam - 248/260 .658/.660 114
ported heads
fast 102 intake
ported throttle body
1 7/8 long tubes with high flow cats

i think its suppose to be 12.1 WOT and 14.9 Idle

generally at wot a good a/f is 12.9-13.1. From what I seen, the LS7 seems to like 12.5-12.6

12.2-12.8. Some cars like it richer, some leaner. Mine is dialed in around 12.6.

I prefer to keep the LS7 stuff around 12.5

Also depends on where you are measuring the a/f at. If measuring from a w/b 02 bung in the header, I always shoot for ~12.5ish. I do favor conservatism in my tuning though.