95 Ranger 3.0 2x4 automatic. Moisture smoke out the exhaust just like blown head gasket, performed pressure test on cooling system, everything fine,compression check, everything fine. not running hot, not skipping, disconnect exh behind CAT smoke stops instantly, install NEW muffler and smoke is back. disconnect and it stops again. truck is showing a code 335 which is high voltage at the EGR valve. is this the cause? used exsisting exh pipe, just changed muffler. tailpipe is very black with soot.