One problem related to gas recirculation valve (egr valve) has been reported for the 1999 Lexus RX300. The most recently reported issues are listed below.
I own 1999 Lexus Rx300, since February of the last year, I had numerous problems with the car's engine (it has sludge), transmission, emission system, and over use of gas per mile. First problem started during the first month of my ownership and since that time the vehicle has spent weeks in auto repair shops. Lexus dealer and others charged me lavish fees but never fixed the problems and Lexus dealers even never admitted that serious problems existed.