Considering what you did with the "Slacker Edition" a maximum HP Viper should be real close with its extra acceleration and top end speed. Also thinking a R8 would be very close, especially considering your time with my "Grüner Walddrache", since their meant for high performance handling unlike that land yacht.

What I really want to see though is you trying to beat 6 minutes in a Mustang, any Mustang! Since you can get a FF SRT4 around the ring in approximately 6:30 I'm thinking you should be even faster with a proper Mustang, question is how much faster? If you want I'll try tuning a couple for you...