After
driving the RX 300 for one year I'm glad I made this mod. Actually, I bought
the RX in Dec and by Mid Jan I just had to improve the heat flow to the driver's
side foot area. Maybe it's just me, but I like warm feet. Heat Flow
Improvements
to the Drivers Side Foot Area
[Difficulty Level = 1]
After
driving the RX 300 for one year I'm glad I made this mod. Actually, I bought
the RX in Dec and by Mid Jan I just had to improve the heat flow to the driver's
side foot area. Maybe it's just me, but I like warm feet.
Especially in a situation like the other day (Dec 27, 03 crossing through the pass at 15 deg and snowing). After standing in the snow and the wifey snug and warm in the RX300 snapping the pic from the open window, I needed to warm up the feet a bit!
Locate
the driver's side heat duct.
Use your mouse to "roll over" the pic below, the duct to be removed is circled.
You can easily see the duct by looking up under the dash on the driver's side just to the right of the steering column.
First Latch
Loosen the clamp on the left side (arrow). Move the clamp down and to the left
(below). Don't back out the screw all the way. If you drop it behind the plastic
kick plate on the right side of the foot area, it is gone forever!
Second
Latch
To get the duct out there is a second latch on the right side of the duct that
has to be pried out a bit with a screwdriver.
It is shown below after removal so you can get an idea of what it is like. You can't really see it clearly when the duct is attached, so this is the best way to show it.
Remove some of the air flow restriction
Once the duct is out, I've cut about an inch off the long narrow front opening, left (rollover pic). This offers a bigger opening and less restriction to the air flow (you get more air flow). If you are uncertain about how much to cut off, cut a smaller amount and try it to see if it is improved to your liking.
Cut the restrictor off the short tube. Half is shown
in the pic below.
These cuts were made with a fine tooth hacksaw.
Restrict/slow air flow to the passenger side
As an addition to shifting more air flow to the
driver's side, I further restricted the flow to the passenger side with a temp
(removable) plug made of a paper napkin (roll over pic). Since the wife always
complains I keep the temp too high (what else is new?), decreasing the air flow
on her side was not a 
problem.
This helps push more air to the drivers side. There are 3 openings here. I have
closed the biggest one, you may want to select a different combination of the
three.
Should we be driving and I get a complaint, I can easily reach down from my position (pull off the road first and put the vehicle in PARK) and pull out the plug and we're on our way!
Now, there are also the warm air vents under the front seats that bring warm air to the floor of the rear seats to warm the kids toes. These too can be restricted to increase the air flow to the front.
Good Luck!