Just purchased an 08 TL w/navi. The car has about 400 miles and I have been noticing that when driving on the highway at 55 to 60 everytime I try to accelerate the car downshifts. Is this normal?

 

100% yes. It depends on how much throttle you're giving it as well. If it notices you're trying to go from 55 to 75 fast, it will downshift for you as leaving it in 5th gear and going from 55 to 75 could take longer then you would expect.

 

kasendorf- here's a recent thread that addresses similar issues to the ones you present. You prolly haven't learned to use your "Search" button yet

https://acurazine.com/forums/ramblings-12/post-your-fave-firefox-extensions-165329/

 

Are you certain it's actually a downshift, or is it just the converter coming out of lockup?

 

this is a case of owner needs to read the book- lots of good tips in there besides basics
Find out about traction control now before it activates one day and freaks you out