I am so tired of the skip.

I bought my car in Oct. 08 and sometimes it skips. I know there have been a lot of skip threads but I can't seem to find one that will work for me.
My car is a stock 1995 Mustang GT with 5.0 and automatic transmission. Well it does have the 4:10 gear.
Sometimes it skips. Most of the time at cruising speed when I am trying to look cool.

It is like a steady random hesitation. When it does skip there is a put put sound mixed in coming from the exhaust. You can floor it and it will go away until the motor catches up and levels off then it comes back.
Sometimes it does it when it's cold sometimes when it's hot. I may drive to town to the store and everything is fine then skip most of the way home. It may go a few days without doing it then do it a few days in a row. Most of the time it only last a few miles.
I have changed plugs, timing, cap and rotor, cleaned throttle and changed TPS. Plug wires look new but I am changing them next. I have ran several bottles of STP through the fuel system.
Any thoughts on this? I hate to just keep swaping out parts.
Thanks
Mike