2001 lexus rx300, firewall

Long time reader, first time poster. Great Website by the way. I need help finding a hole in the firewall of a 2001 Lexus RX300 to run a 4 gauge wire through. My customer would rather not have me drill a hole in the firewall unless it is 100% neccessary for the installation. Also I need to tap into the rear speaker wires for an amp interface adapter. I have searched and only come up with wire codes for an IS300 and i would like to make sure that the color codes are the same, along with the factory amp location(passenger upper kick panel). Thankyou for any help.

     WIRE          COLOR          POLARITY          LOCATION           Battery          WHITE/ YELLOW          (+)          RADIO HARNESS           Accesory          WHITE/ RED          (+)          RADIO HARNESS           Ground          BLACK          (-)          RADIO HARNESS           Illumination          RED / BLACK          (+)          RADIO HARNESS           Dimmer          RED          (-)          RADIO HARNESS           Power Antenna          YELLOW/WHITE          (+)          RADIO HARNESS           Amp Turn On          YELLOW/WHITE          (+)          RADIO HARNESS           LF Speaker (+)          WHITE           LF Speaker (-)          ORANGE           RF Speaker (+)          YELLOW           RF Speaker (-)          BROWN           LR Speaker (+)          RED           LR Speaker (-)          GREEN           RR Speaker (+)          BLUE           RR Speaker (-)          BLACK           Amp Location          MOUNTED TO BRACKET IN RIGHT SIDE OF TRUNK           Steering Cntrls          YES                     THIS VEHICLE MAY BE EQUIPPED WITH OPTIONAL ONSTAR® TELEMATICS EQUIPMENT. USE AN APPROPRIATE INTEGRATION HARNESS OR INSTALLATION PROCEDURE TO ENSURE PROPER FUNCTION OF THIS EQUIPMENT.           Speed Cntrl          NO           Radio Security          YES

Thanks man that helps alot! Anyone have ideas on a hole in the firewall? I have heard something about a hole near the brake pedal.