I am under the notion that it would harm the CAT and O2 sensor. However, since no smog required in CA for 5 years for a new vehicle, so which means i'm home free to run catless till 2008.

I plan on buying a Perrin testpipe with o2 sensor simulator, so in this particular case, i've taken out the only two things a leaded gas would hurt the engine with.

My question is, are there other harms associated with leaded race gas?

 

The front o2 (in the o2 housing) will be affected. The o2 simulator is used to fool the rear o2 into thinking that the cat is still there. The front o2 is the sensor that gives feedback to the ecu for closed loop operation. Prolonged exposure to leaded gas will ruin it at some point. How long? Dunno. Leaded gas can also clog your injectors over time.