I have a 1995 F350 and can not get the check engine light to turn off. The code it pulls up is P0470 (exhaust back pressure sensor). I have replaced it and the tube and also cleaned the fitting in the manifold. I have tried to reset the code even after the new parts and nothing. The truck still runs great but I need the light off to pass emissions. The only thing I can think of is replacing the PCM. Has anyone else run into this problem before or know of something else I can try before I buy a new PCM? Any help would be great.