While Berryman B-12 Chemtool Fuel System Cleaner (part #0116) is compatible at reasonable concentrations in excess of the maximum recommended dosage of 1 oz/gal, it is not an ideal solution for the problem you described. The best course of action depends on what the underlying problem with your Lexus is. Catalytic converters are “self cleaning” under certain conditions and should always last the life of the car. If the “guts” are physically intact and there’s just some build up on the catalysts, then running a good fuel system cleaner can help tremendously. That said, making sure the engine is properly tuned is also key. If, for instance, the unburned HCs persist for long enough—this can happen with old or bad spark plugs, cracked plug wires, dirty combustion chambers, etc.—then the cat can get too hot and start physically breaking apart over time. If this happens, no cleaner in the world can fix it and the component will have to be replaced. If your Lexus has failed a vehicle emissions test or your “Check Engine” light recently came on, try Berryman Emissions Pass Protection (part #0212). This is a premium fuel treatment that reduces hydrocarbon (“HC”), nitrogen oxides (“NOx”), and carbon monoxide (“CO”) emissions in part by cleaning up fuel injector, carburetor, intake valve, and combustion chamber deposits that can contribute to high emissions. Additionally, it incorporates a combustion catalyst that helps reduce high emissions. Best of all, the product offers a money-back guarantee.