Subaru Impreza STI Type RA '05, 550pp N3 @ Fuji - 1:54.5 in free run.
I've seen a 1:53.8 in a race, but while I thought I was out of the draft for that lap I must have had a bit of a pull as I've not got close to that since. On a good day I can do around 1:55.0 fairly consistently, best total race time 9:37.
This car can go faster though, last night AyrtonSenna must have been putting in around 1:52.5 to get a total race time of 9:25. That sounds about right, when I know an AWD car and track fairly well I'm usually about 1/60th slower than the aliens.