Bought a 2005 RX330 from a local non-Lexus dealer couple months ago. It was auctioned because the previous owner failed to pay the bill. Recently during cold start, the idle RPM is between 1.5 - 2 and the engine roars quite loud. In addition, there's a slight smell of burn (not raw) gasoline coming out of the tail pipe. Currently it has 21k miles. What could be the problem? Is the problem covered under Lexus basic or powertrain warranty? Thanks.