p401 egr problems on 1998 Oldsmobile Intrigue

keep getting a P401 code. I just replaced the intake manifold gasket, and a couple days later this code started. Can clear it, but a couple weeks later the code will come back. Seems to run a little rougher than before. Do I have something in the egr tube. I replaced the tube from the intake manifold when I did the gasket.

Asked by for the 1998 Oldsmobile Intrigue
Symptom: Diagnostic Trouble Code P0401

System: Emissions/PCM/Fuel

Codes: P0401

Problem: Positive Crankcase Ventilation Valve (PCV) is missing. Oring for the PCV is missing or the incorrect PCV valve was installed.

Test & Fix: Remove plastic cover for the Positive Crankcase Ventilation (PCV) Valve and inspect Oring for being missing or damaged. Verify the PCV is the correct application or if the upper intake has just been replaced make sure a PCV valve has been installed. Replace the O ring or PCV valve as necessary to correct the condition.

That is probably right. The pcv sits under the map sensor and I don't think I put it in tight. Thx a lot!!!