Its not possible to run lean at part throttle or even idle since the computer keeps a 14.7:1 right? Its only WOT that you can run lean correct?

 

The computer can only correct so much, then if those limits are exceeded, you could run lean. If you installed smaller injectors than the computer thinks is installed. A lean condition could be generated as the computer tries to richen up the mixture, but runs up against the wall in its BLM table (I think).

Perhaps if you installed a particularily radical camshaft that sent out alot of unburnt fuel into the exhaust stream, the computer might also try and lean you out to get what it thinks is a good mixture, that would leave you in a lean condition.

Under normal (near stock) you would not encounter a lean condition at idle/part throttle. You shouldn't encounter a lean condition at WOT either, that is unless you have some sort of Power Adder in the mix.

Hope this helps

LWM