So my dad'* forrester is currently throwing a p0170 "fuel trim malfunction" doesnt specify rich or lean, but the fuel trim was up 17% i cleared the code and KAM, gave the car a tuneup it needed, but it came back, so i started some diag, the o2 sensors are new, and switching, my first thought was vaccum leak, no such luck, spent a whole day going over every single vaccum line and after much tests i am 100% sure there is no vaccum leak, now my tools are pretty limited at the moment cause i'm at school, but im basicly down to fuel injectors, a bad sensor, or an exhaust leak, i just wanted to know if anyone had any other suggestions, at the moment im pretty sur eits an exhaust leak tho, the thing sounds like it has one, but it'* sounde dliek that for as long as i can remeber so i dont know if it normally sounds liek it does

p0170 is bank 1, try swapping the o2 sensors if they are the same.

bank 1 is the only bankk, theres only 1 set of o2 sensors

Seems you are on the right path.