1991 f150 5.0 seams to run rich and builds up until running a little rough at the stop light. Idles at 600-700. I actually power brake at stop light to aprx 800 just to keep it from building up on fuel. Maybe not fuel buildup but seams as such. Injectors maybe? I time the 5.0 at 10 degrees and as soon as I plug in the spout the timing starts to jump all over, to between 5 to 20 degrees and does so very erratically. I guess my question is: can my knock sensor be causing this erratic timing behavior. I've replaced about everything else. I have a parasitic drain that needs diagnosed so I'm unable to get codes due to disconnecting the battery. Going after that today and maybe it will help. The eng does have a small "knock" that I would detect if I were a sensor.