All makes and models of cars are susceptible to this. The general Lexus all-models TSB is EG001-03, title SULFUR ODOR FROM EXHAUST, published Feb.24, 2003. The only corrective procedure is to try a different source of fuel, as the source of the smell is from the fuel itself.
Replacing O2 sensors or catalytic converters will NOT reduce the odor.
I personally recommend using a Top Tier certified gas, of at least the minimum recommended octane specified for your car. See http://www.toptiergas.com/retailers.html
for retailers in your area.