Rough Idle

[snozzau]

Guys,
I have a very annoying problem with the idle on my XR6.
Sometimes it will idle as smooth as silk where other times it seems to rev up and
die down.
I have changed plugs & leads ,cleaned the injectors,changed the air filter,cleaned the throttle body and IAC.
Had a look at the fuel filter but it looks new.
After reading private9 post about oxygen sensors I will probably change that too but I dont think that will help my idle problems.
Ideas ???????
Scott