So, my forester is giving me issues. above 3k+/- rpm it hesitates and loses power, makes passing a bitch. my first instinct is telling me that the A/F sensor is bad, when I first bought the car years ago this was the issue, and it only affected above 3k rpm but if i remember correctly it produced more of a bucking than just a hesitation. also, it gave a CEL. I have no CEL and no pending codes at the moment. And I dont want to drop $100 on a sensor if im not positive it will fix it, funds are tight at the moment. If it only gave me a light i could figure it out but no such luck. I have attached some screen shots from my torque app showing the readout of the o2 and the A/F sensors. I believe they are fine and did a comparison with a 03 outback 4cyl tonight to see what his showed and the readout was pretty much the same (he doesnt have any issues). Another symptom is that the problem is more prominent when the engine was to op temperature and it gets even worse if the outside temp is above 70-75 degrees. I let the car get to operating temp and unplugged the rear o2 sensor first and no change at all, of course it gave me a CEL after that but I knew the problem. Then, I hooked it back up and unhooked the A/F sensor after warm up and zero change as well. hooked it back up and still at square one. Looking online and I get a huge variety of results. from the o2/AF sensor, to throttle body. to needs tune up (it could use one, but I checked the plugs and they arent terrible enough to cause issues), to knock sensor, to clogged cat, etc, etc, etc,etc. I have to start ripping into the wifes civic this week and replace the headgasket so I cant afford to have both vehicles down. Any suggestions? All screenshots were taken while driving and accelerating and hesitating. the ones where the o2 and AF are flat lined are while the car is coasting in gear with neither the brake nor accelerator pressed.