hi all , i have trouble with the haynes book, not enough pictures, i'm not used to all this electronics in a car and never thought to try to fix one.

i have a zafira 1.8 dohc ecotec 2001 auto z18xe or z18xel ??, i have an error - p0170(feul trim bank1 ???), replaced the oxygen sensor on the exhaust, but still having trouble, bad idle when cold, missfires on the odd times, loss of power when the revs are up and above 2500, mucking up gear change because being an auto, so, should i replace the o2 sensor on the cat. i cleaned the MAF, worked with alittle improvement, i have disconnected the front o2 sensor on the cat, the car was the same, so does that mean that i have found the problem.

i just really not sure what to do now, haynes isn't all to clear, the advice from the forum has being englightening, but not really clear with all the terms being used, i'm a bit of a laymens man really, nice and simple like my old MG, i have read through the forum, and seen many answers for other people, the list of things it could be: cat, cat o2 sensor, after cat sensor, Maf, ECU.
i have an elm327 that i have plugged in, but i have little understanding of everything on it.

help is all i can say.