I would doubt the EGR is causing this, as the EGR really only operates 'when needed', which is basically rapid speed up/down, and at crusing speed (over drive, or 4th on non-equiped).. and many folks have bolted a plate over the egr valve opening completely removing that part of the system (not technically legal in areas where you have a smog inspection.) But, to answer your question,
check
this link
look for the pages for the EGR system (that's the renix fuel injection system manual)
are you talking the EGR solenoid? The guy on the driver fender side of the engine compartment? If so, a quick and easy check (mechanically) would be to :
while engine idling and running crappy, use a screwdriver to push the linkage in towards the engine, if it smooths out, you either have a stuck (partially?) egr valve, or a blown solenoid (which is what I had).
a dirty test (not testing the electrical capability of the solenoid) is to :
1) Pull all vacuum lines off of it, unbolt from frame.
2) on the inlet (side towards headlights) blow in some air
3) (double check the above link for which port) air should escape from one of the two outlets, plug it with your finger. if air continues to escape from the other outlet, your egr vacuum solenoid is blown. If this is the case, replace the vacuum tube boot on the other side too, it most likely ripped internally, as well as the factory plug for the unused outlet (it has a seal which wil seperate too.) I got some short vacuum unions from autozone and placed them instead of the boot on my connectors, and used a new plug too.
if you have to go to a dealer, it's $105 plus tax for the part, if you go to a junkyard, they will have no clue what it is, and will charge you around $20.
hth
