this part is just the fore-info, the actual question is in the next paragraph: i read my codes with someone else'* tool on friday and got two error codes, one the infamous p0171 (bank one too lean) and [can't remember the number] evap control problem. my shop teacher told me they would be related, and i found the evap problem and fixed it. then after reading on here more, found that p0171 is caused by corroded battery cables? so i cleaned it as good as i could without a wire brush.

so, after reading the threads about code reading, i see a lot of mention on "clearing the codes". did i miss something with the scantool? cuz my CEL is still on.

Disconnect the battery for 30 minutes if you didn't clear it with the scantool. If the light comes back on, you still have a problem.

An evap problem is usually vacuum related. HOW did you fix it? If you have a vacuum leak, you will run too lean. Vacuum leaks pull in air that is not metered (seen) by the MAF sensor.

the line that connects the evap canister to the fuel tank was pinched under the motor mount, so i cut out part and replaced it with some rubber hose and clamped it on.

i have had a vacuum leak, and it was idling rough, but i sealed it with weatherstrip and the rough idle went away, and eventually the CEL went out.

i have the same two codes. P0171 and P0441 , i think it was, i replaced all my vacuum lines except the one you had mentioned under the motor mount, but i have not tried to fix the 171 code yet, havent had any time, still have the 441 code too, incorrect purge flow from evap canister..