ive replaced gas cap , checked every line imaginable. i can drive the back roads all day with no light. once on the higway above 70 i get it. once the car is off and back in the garage , i have no light when i take it out again

And... the stored code is... ?

I'll go out on a limb and suggest it's got to do with a malfunctioning EGR solenoid.

quote Originally posted by Patrick: ... I'll go out on a limb and suggest it's got to do with a malfunctioning EGR solenoid.

My thought as well.
To expand on the EGR solenoid thought, also check for vacuum leaks (which turned out to be one of my problems).
There are two barbs on the bottom of the throttle body. The EGR is the smaller of the two. It uses a 90 degree rubber fitting that the hard plastic vacuum line plugs into. From there, the line goes to the EGR solenoid, and then back to the EGR valve. ANY of those lines - or terminations - can cause a vacuum leak. Most of those fittings are at least 35 years old by now, and many have deteriorated.