1998 Olds Intrigue GLS & EGR

I've replaced the EGR valve once myself (about 1yr.5 ago - it intermittently came on when cold then would go off in warmer weather - strange), and then had a mechanic replace it after getting a Service Engine Light again (not sure of the code #, but it points right to the EGR). Unfortunately this diagnosis is not correct - the light came back on only after minutes from the service shop. Any ideas on what else we can look at?

I am having similar issues trying to get a new smog certification. I was recently informed that if you go to AUTOZONE, you can now use (free) their ODB and check the service engine soon codes. I did and it was GREAT!!!! It told me I had misfire on #4 & #2 so I replaced the whole set of spark plug cables and the light has stayed off and engine runs much smoother. However, after retesting it for smog I failed again. The new info I received from a mechanic friend is that..."if there is any carbon build up around the valve, it sticks slightly but not enough to trigger the sensor" So..I hope the tip about AUTOZONE helps...
My problem is that I am unsure about what kind of EGR valve I have. I found directions on how to test it to see if its bad but not sure about my specifics. I also have a 98 Intrigue, any info you could offer would be greatly appreciated!