tl;dr: Don't let your Dad talk you into buying a car that you were going to walk away from.
I'm ready to push my car off a cliff. I drove to work fine yesterday morning. On the way home though the car felt "off"...it started struggling to keep pace with traffic and even sounded a little different with a hiss. When it would downshift into 3rd or 2nd gear to try and keep up on hills, i could hear the hiss more prominently and the car would just not move. Engine temp gauge was fine, transmission downshifting fine + warning lamp/gear indicator solid green and not flashing (counting my lucky starts I haven't had that happen yet...)
When i got home, i scanned for codes. No changes there...I did get a P1491 (insufficient egr valve lift) a month or so ago. That was still there but nothing new.