first off it depends if you have a squre bore or a spread bore (figure that out first) then the size is between 600-650 try not to go higher than a 700 because then you will most likely get vacum leaks and the air intake for it will be crap. hope this helps!!!!
carburetor
160 horsepower - 2 barrel carburetor 180 horsepower - 4 barrel carburetor
The 2009 Lexus IS-350 has a 3.5 L base engine size.
The 2007 Lexus IS-350 has a 3.5 L base engine size.
The 2011 Lexus IS-350 has a 3.5 L base engine size.
The 2014 Lexus IS-350 has a 3.5 L base engine size.
The 2006 Lexus IS-350 has a 3.5 L base engine size.
The 2012 Lexus IS-350 has a 3.5 L base engine size.
The 2010 Lexus IS-350 has a 3.5 L base engine size.
The 2008 Lexus IS-350 has a 3.5 L base engine size.
The 2013 Lexus IS-350 has a 3.5 L base engine size.
The 2013 Lexus IS-350 has a V6 engine.