Saturn L200 - P0420 & P0172

I have a Saturn L200 with the 2.2L 4-cylinder Ecotech engine. I just replaced the original converter (which was plugged) with a new unit from CATCO. Before this, it was at the Saturn dealer to have the timing chain and cylinder head replaced (Ecotech owners know about this nightmare). So I get it back and within a month, my converter starts rattling and then plugs. I thought the Saturn dealer might have done something to cause this. Anyway, I finally scraped enough together to buy the new cat and install it. The first thing I notice is that the converter seems to smell awful hot after running the engine for awhile (the engine temp gage is normal, not hot). The pipe from the exhaust manifold to the front of the converter is purple (is this normal??). The SES light was on before (I never had the codes checked or cleared). After replacing the cat, I figured they would clear, they have not. I took it to Autozone and found both a P0420 & P0172 code are on it. I can't believe I have the P0420 with the new cat and could not tell if these codes were stored before I replaced the cat or not. Autozone also would not clear the codes for me because of some liability issue?!?! This car has 142,000 miles. The only codes I have ever received before were due to a gas cap issue. Any ideas would be much appreciated.

Thanks,
Dean

Your P0172 is "System too rich, bank 1". Your O2 is sending the computer a reading that indicates unburned oxygen in the exhaust. That condition may be bad enough to overwhelm the converter and cause the downstream O2 to send the same signal. This too rich condition may be what ruined the original converter. I would start by checking the basics. How long has it been since you installed new spark plugs? Air filter? PCV valve? Other than that, I would go back to the dealer and explain to them what has been happening, and make it clear that all this mess started after they did the cylinder head/timing chain. Don't go through this headache when it is very possibly their fault!!