The car: 1994 C280 with 95,000 miles.

I just did my emissions certification on the car, as we have to do every two years. I passed, but when I compared the results to the test from two years ago, my HC ppm had increased dramatically. I had 17 ppm at idle and 33 ppm at 25 mph (I'm allowed up to 55 before I fail). Two years ago it was 0 and 0. What could cause such a large increase in HC? I brought the car into the test hot, having done a 20 mile run up the highway to heat it up for the test. I have a failed air pump, but as the car was started hot (it was on the test apparatus within 5 minutes of arriving) I don't think that has anything to do with it. I also intermittently get a code for a failed purge valve, but I just clean it out with Arthur Dalton's trick when I get the code.

Any ideas? If I increase the same amount in two years, I'll fail then. The plugs have less than 7,000 miles on them, as do the plug wires/boots and the MAF.

Thanks,

Jonathan