1997 Cutlass Supreme Trouble Codes P0401 and P1406

I have a 1997 Olds Cutlass Supreme that's giving error codes P0401 and P1406. When I replaced the EGR valve, this "brown Gravy" was in the inside of the hole going into the engine, as well as in the EGR valve at the bottom. I cleaned it out as best as I could wqith a rag and screwdriver. I'm still getting these codes.

The car has 165k miles on it. I've already spent $200 on it. I hate to spend much more on it, but I can't renew my tags here in Tenn without getting these codes cleared and fixed. Any help would be appreciated. I have an appointment with another mechanic Thursday morning...to maybe clear the codes. I can't figure out how to do that either.

Thanks