05 TL poor performance

Hi all, I am new here. A member in my family just bought a 05 TL with 150,000 miles on it in very clean condition. She told me that it doesn't have very much power and I was rather surprised as I have two friends that have owned these cars. She also told me that she was using regular gas in the car and I thought that this might be the problem. Upon refilling it with premium, the situation has not changed, Any ideas on what to look for would be greatly appreciated!

Thank You