HC: As for the high hydrocarbons, your car may be running rich. It can be rich due to the fact that you have a vacuum leak somewhere. Or your engine temp. is too low. Or you have an injector misfire. Or an ignition misfire. I don't know what your situation is but you might what to check these. Here is the tricky part of HC emission: anything can cause high HC.

CO: For the high reading of Carbon Monoxide, here are a few things that can result in high CO: leaking fuel injector, high fuel pressure, saturated charcoal canister, the PCM thinking that it needs more fuel, or a contaminated crankcase that causes the PCV valve to throw back fuel vapors into the intake which will richen the air/fuel mixture.

NOx: Sometimes a clogged or stuck open EGR valve will cause the high NOx emissions. Since EGR system only operates at cruise, it cannot cause high NOx emissions at idle. A very retarded timing will also raise NOx emissions and raise the combustion temperatures along with a large decrease in the engine's efficiency. A slightly retarded timing will reduce NOx but it will also slightly reduce the engine's efficiency. Doing the opposite like advancing the ignition timing will increase NOx emissions.

Since you just had a T.belt/waterpump job and a head gasket replaced you might want to check your ignition timing. Make sure that the technicians we're off a tooth on the cam gear. Also make sure that watepump is working by checking the engine coolant temp. It would also help if you check you cat. converter and make sure that it is working properly. You can easily check to see if the cat. converter is working properly by using a laser beam guided temperature gun. The temp. should be a lot hotter after the cat. converter.