Toyota Repair: troubleshooting, speed tranny, o2 sensor

Question
I have a 1992 4runner.  Straight six 4wd.  It starts usually with ease and once started, maintains a healthy idle.  It has a manual 5 speed tranny and when I press the accelerator and release the clutch the motor acts as if it is not getting fuel or it is being smothered/bogged down.  The problem is noticeably worse when shifting from second to first to the point of killing the engine.  I am leaning towards the fuel filter or oxygen sensor.  What are your thoughts?  If you should happen to agree could you advise a location on the fuel filter?

Answer
A failing O2 sensor would turn on the check engine light, the fuel filter is a possibility, toyota didn't make 4 Runners with straight six cylinder engines so it is either a V-6 or a 4cylinder, on the V-6 the fuel filter is located inside the frame rail on the right side next to the transfer case, on the 4cyl it is located just above the starter on the right side of the engine.