Milwaukee Mark

I have an '87 GT 5.0 HO..automatic (everything stock) When I first got it it ran fine .The first day I got it I replaced the cap,rotor , plugs , wires, oil change, air filter. My problem came about about a month ago, it would run fine some days and others it would get a really bad idle fluctuation and then shut off. It would start right back up , no problem and would be fine. As time went on it eventually started happening more often . I cant get a code off of it so I started to do the idiotic process of replacing parts that could be the problem. (least expensive first) In no particular order over the last week I replaced the following:
OIL SENDER SWITCH (I was told that if its bad it could shut the fuel pump off , hence the stalling) no big deal ... wasn't it .
FUEL FILTER... wasn't it.
FUEL PUMP...nope
Today I replaced the IGNITION MODULE ... doesn't shut off but now when it warms up it idles at 1000 rpm and is running just a little rough.
Any clues..??? I'm gettin tired of not being sure what it is .. but this new "problem" with the high idle has me wondering wtf.?