Wildcat,
Yep, I should change my username. I didn't use backing when I put the vinyl floor in and it has not seemed to have made that much of a difference. With the XJ I did add extra heat sheild under the carpet because the floor used to get really hot from the transmission. But has not been an issue with the tacoma. The floor was a real PITA to install, not sure if it was the fit not being correct or my lack of install skills, but it is far from show truck install, and works for me.