I have an 06 SR5 with port installed leather. My seat heaters have a 3-position toggle switch for each of the front seats. The middle position is "off", the forward position (designated with 2 horizontal lines) heats both the lower back and seat bottom, the back position (designated with 1 horizontal line) heats just the lower back. There was a card in my glove box that described the operation of the seat heater. It states that you can cut a wire loop under the seat to make the switches control the temperature instead of which parts of the seat receive the heat. If you cut the wire loop, then both parts of the seat are heated and the switch just gives you 2 different temperatures.
On my 05 (which was replaced with the 06 through the lemon law) the seats didn't get as hot as the 06 nor did it heat up as fast as my 06. It seems that it was improved. I think the Limited has a wheel type control for the heater, but I might be mistaken.
If you guys don't have this card, I can type the info in a post.
Doug