1999 Saturn SL2 high idle then low then high... chk engine light finally came on... please help (more details)?

It was cold about 35 degrees outside so i let my car idle for about 20 minutes. then it started acting really funny. The rpm would cycle between 500 and 1500 rpm in very rapid succession and then after about 20 seconds of doing this, it would spike up to about 2500-3000 rpm. after this continued for about 5 minutes, it finally threw a DTC. P1404 (EGR Valve) and another code im thinking to do with TPS. I drove around and at a stoplight, it finally kicked into 4000 rpm for about 3 seconds then everything went back to normal idle conditions, as if nothing ever happened but the chk engine light still on. So it sat overnight and the next morning, the chk engine light was not illuminated and it worked fine in the morning. Then, driving home from work this evening, the check engine light came back on and now it just spikes to about 2500 rpm when i push the clutch in (its a 5 speed manual) with no "cycling" like it was doing the night before. Anyone know what this could be???