Car runs rough at times others perfect.

My 99 dodge durango 5.2 liter v8 will
run great at times. I have a check
engine code. About 50 come up
including all o2 sensors. Then at times
the check engine light goes off every
time I go to get it read.  Cat is fine and
plugs wires cap and rotor have all been
replaced. Fuel pump as well. Fuel filter
and battery. My cables have been
cleaned at least once a week for the
last month and a half. No that doesn't
cause the check engine light to do its
random Ness.  I was told to check and
clean all grease, dirt and oil off the
motor. Could be causing bad ground.
Another mechanic said it could be the
fuel pressure regulator. Or I need a new
p.c.m. as my door locks won't work as
well and sometimes I hear a clicking
under the passenger dash. I believe
this may be the cause. Any more input?