So the K5 is idling high when cold and has +30psi of oil pressure at cold idle. When warmed up, it idles low and has ~15psi of oil pressure (on the gauge). The truck is also missing pretty badly, especially noticeable when its warmed up and idling low (the engine shutters and shakes the truck sometimes). I've replaced the plugs, wires, air filter, pcv valve, TPS, both thermo sensors, and....I'm pretty sure that's it so far. I also ran a can of STP fuel system cleaner and the STP gasoline treatment with the last 2 tanks to see if it might be a dirty system...no difference. I just changed the fuel lines out, but did not change the filter...would it be a good idea to change out the filter as well? I don't think the fuel injectors have been rebuilt/replaced ever (it's a 91 with ~147k mi). Any thoughts?