as i mencioned before, i follow religiously the guide stuck at the forum, cause i know it works, and i follow it 2 times, printed list, and crossing with a pen 1 by 1 all of the items, first when i pass the game and second time re-cheking all places again, (and no items at the auction), but the achieve doesn't pop up.
I'm not saying that the guide is wrong, i've done tons of achievements like this (assasin creed, gta IV, all call of duty's collectibles, full blue dragon) and always doing for the first time, tons of printed guided marked, im always sure what i take and what not, and save game in separately slots frecuently.
This is (and for the people who follow splitplaytru and didn't doing too) cause i think the achievement is bug for some people.
Anyway i will follow AGAIN all places these days and if doesn't work, i will do new game+ and re-do again with 3 distinct printed guides and splitplaytru youtube's guide, and then i will come back and tell all of you.
I know, i'm crazy... it's only 20G, but... NOW is PERSONAL