air/fuel ratios definitely differ from setup to setup. I just recently tuned an LS where the guy had dome some very extensive modifications to his head and combustion chambers. This resulted in the car not wanting to idle consistently at anything less than 11:1.

VTEC engagement (when you have a vtec motor) is best determined on the dyno... make a pull with a high engagement point and then do the same with a low engagement point. Overlay the 2 torque curves and set the engagement at the point where they cross.

One thing to note is that a properly setup fuel table is an exact reflection of the shape of your torque curve... if you tune a motor at WOT with a dead-flat a/f ratio throughout the entire pull, and then you graph your fuel map, it will mimic the torque curve shown by the dyno. A fuel map is basically a map of the volumetric effieciency of your motor. Many standalone systems, when plotting 3d graphs of fuel tables, label the axis by: rpm, load and VE. Something to think about...

Consider fuel nothing more than thermal management. An ideal a/f ratio for all load points is 14.7:1 (on gasoline). This does not work in the real world because a lot of heat is generated by a motor. This heat, if not properly managed, will melt pistons, etc.. The extra fual over 14.7:1 is used to absorb the heat from the combustion process to keep the motor from melting itself.

There is very little (if any) power to be had from general a/f ratio tuning. You just want to setup the fuel table so that you have enough fuel to properly suport the car at all possible load and rpm breakpoints. Power is made in with ignition timing. Motors are also destroyed by improperly tuned ignition timing. The goal is to measure the torque output of your motor and advance the ignition timing until just before MBT (or until you see knock on the plugs from insufficient fuel/insufficient fuel octane rating/etc.) This can only properly be determined on the dyno. It is absolutely essential to read spark plugs very often when tuning. I pull a spark plug after nearly every single dyno pull to check for detonation, etc.. The spark plug is your window into the motor's combutstion event.

Typically, I setup a conservative basemap (with conservative ignition timing) and tune a car on the street first (when possible with a streetcar). The street tuning is there to basically dial-in idle, free-revs and partial throttle (for gas mileage and overall driveability), cranking tables, corrections, etc. Depending on the setup, I'll do some WOT pulls to dial in the a/f ratio where I want it (to save time on the dyno). I only make small fuel table adjustments on the dyno, if needed.