01' Gs 300 Not Performing To Potential

[momaz'wip]

My mother owns a 2001 gs300 which has about 119k miles on it, and i had to drive it the other day, and it was slower then my volvo s70glt. I think some of the hp loss might be from my mother putting 87 octane instead of 91 but it feels like the car is revving high but not going anywhere. The car is stock but i tested the 0-60 and it was ~9 seconds. any ideas of why it is so slow?