I just got back from getting a smog check, and my car failed. Any idea on what the problem is? Here are the failed items:

2500 RPM Test
HC PPM: 208 (should be < 130)
CO %: 1.15 (should be < 1.00)

Idle Test
HC PPM: 287 (should be < 100)
CO %: 2.65 (should be < 1.00)

It also failed the EGR test.

The car is a 1993 300E 2.8 w/ 175K miles. I replaced the 02 sensor about 20K miles ago. The only other noticable problem the car has is a slightly rough idle.

So what is this? Bad EGR valve? Defective O2 sensor? Gas milage is still good...