I have a 1997 chevy lumina with the engine light on.The code says there is lack of flow with the egr valve. I replaced the valve but have a milky oily substance in the new one. what is my problem? I also replaced the upper gaskets because there was a anti freeze leak on that same corner of the engine.

SOURCE: how to replace EGR valve on 99 Chevy Tracker

Take off your EGR valve and clean it out with carb cleaner also
grease tyhe little screw thing in it,,, u will c what i mean if u take it apart. carbon builds up in the chamber. it is located at the back left side of your engine and is a bit of a pain to take off. this should save u the cost except for the cleaner and labor. i had the same problem cheapest i found was 90$ on ebay.

SOURCE: Service engine code indicates EGR valve.

You could have a restriction in the egr ports. remove the valve. Plug the holes, start engine. 1 hole will be blowing out exhaust, the other will have large vacuum.

SOURCE: OBD code P04001 Insufficient flow, I changed the

did you clean the EGR passages? take the valve back off. one hole will have exhaust, the other should have strong vacuum.ususally the passage gets plugged with carbon, from the valve to where it goes into the intake manifold. you may take a wire and carb cleaner to clean the passage.

SOURCE: Have some white, milky looking substance on the dip stick

I'd be tempted to live with it depending on whether the vehicle is using coolant on the assumption that it is condensation causing the saponification of the oil. If the Lucas oil treatment caused the pressure to rise so dramatically I would suspect that some crud has come adrift and lodged in the pressure sender.
The chance that the cylinder head is cracked would be more rare than a leaking head gasket both of which could possibly be tested by a leakdown test of individual cylinders.
The water has to come from somewhere.
Does the soap go away when the engine is warmed up?

Testimonial: "Good point on the pressure issue, not using coolant. Dip stick had rust on it and so did the inside of the fill cap. Hot or cold white on the stick."

SOURCE: service engine soon light on, obd says egr valve

You really need a scan-tool to look at live data and test components. If you replaced the EGR valve and you are still getting insufficient flow then the valve wasn't it.
What did it look like inside where the valve goes? What did the valve look like when you pulled it out?
The MAP sensor can affect the way the EGR works.