Book says map sensor voltage high (low vacuum). I think this is related to the EGR valve or does this year (1990) have a separate map sensor. If so where is it. I cleared code and engine service light did not come back on again Yet! Thanks

I may be wrong on diagnostic. EGR flow check is the cuprit. What should I do first.

You have the same EGR valve I do. The little 'mushroom' digital EGR. I'm assuming you don't have a scantool, so you'll have to do it a bit simpler. These usually suffer from a mechanical binding. There'* 3 spring-returned solonoids in that sucker.

When mine threw the last code in June, I simply went in there with WD-40 and sprayed the shafts. Use this as a SOVENT, not a lube. It dissipates too quickly. Also use it to clean out the electrical connector, both sides, and let it drip out.
If this solves the problem, use a hi-temp LIGHT grease or teflon based lube on the shafts for long-term lube.

If this doesn't work, you need to check the solonoids with an ohmmeter. The pinout goes like this:

Imagine the triangle where the harness plugs in as being an arrow to the RIGHT, ie: the longer point goes to the right. Pin A is on the far right, B is in the center, C is top left, and D is bottom left.

a-d should be 20-30 ohms
b-d should be 20-30 ohms
c-d should be 10-17 ohms

If any of these are incorrect, you're replacing the valve.

Much thanks for the response. Looks like I got a project for Saturday. Always something to look forward to with an older car, but I love it so...

Hey thanks all. Took EGR all apart and sure enough one ot them seemed to be sticking Cleaned whole thing up and so far no problems. Thanks again.