could be many problems like vacuum or wiring you may want to spend some money on hooking up your computer for a diagnostic test should only be one hour labor time for this test
The accelerator linkage is binding.
If your engine shakes when you accelerate, you may have a broken motor mount. You need to get it fixed before your engine falls out of your car as you drive along.
The Lexus ES 300 is front wheel drive and the Lexus GS 300 is rear wheel drive
High Pressure Turbine
when you take the car out of drive and put in park the drive mechanism or transmission does not put as much load on the engine so it runs faster.
Lexus RX 350
The 2012 Lexus IS-350 has rear wheel drive.
The 2009 Lexus IS-250 has rear wheel drive.
The 2007 Lexus IS-350 has rear wheel drive.
The 2012 Lexus IS-250 has rear wheel drive.
The 2011 Lexus IS-250 has rear wheel drive.
The 2010 Lexus IS-F has rear wheel drive.