Well it was time to get the Lexus tested for emissions and the CEL had been coming and going for a few months. Every time I would check the code it would be for poor catalytic performance. After some research the conclusion is that replacing the factory cats is an expensive project and a new exhaust system from front to back was in order.
So with some finesse I was able to get the old system out and the new one installed. The OEM system had four O2 sensors, two upstream active fuel management units and two downstream for gross readouts. A cool company called TokenSolutions offers a dual O2 sim for Lexus and Toyota products that keeps the two upstream sensors and elimnates the two downstream without setting a CEL. Neat.