Ok this is the problem lexus fam, I have a 2001 gs300 and I resently did a full major tune-up on it which included the following (new timing belt and timing belt pulley by gates, new idler pulley by gates,new torque master spark plugs and new ngk wires and a oil change w/new filters) I also had to replace mybank2 sensor 1 o2 sensor afterdoing this it ran better but today 3-27-11 I notice it had a sputter when I 1st started the car and while driving I had to almost put the gas to the floor to get power the a CEL came on along with the vsc lights. went to autozone and they pulled a po300 code. i'm thinking the spark plugs aren't worth a damn cause i check the vac holes and there not leaking gas cap is tight and new from lexus. if anybody had this problem please help a brutha out....

 

Check this out and see if it helps you.

http://repairpal.com/OBD-II-Code-P0300