Lingering issues

Well I have been battling the 'System too lean' codes for a while now (http://forums.stangnet.com/showthread.php?t=458298 ) and tried to reset the computer this evening so it could learn the new additions. After trying the reset I immediately noticed a drop in power, I don’t have anything until I get upwards of 3500-4000 rpm, usually referred to as the power band correct? Well before the reset I felt much more power in the lower rpm's and the exhaust had a much throatier sound.

Do you think the lower rpm power was just from the car running too lean as the codes said? How would I get back to running on the lean side? Not dangerously lean, or lean enough to throw the check engine light again, but enough to get that feel and sound back.

How long does it take for the car to learn everything, I'm assuming it's not immediate. Should I reset everything and take a nice long drive, say 50-100 miles up the coast or something?