Moloch is right. I don't see how Bob can win this race for you.
The AI Speedsters are completely maxed out. Notice how you always get 200 points, no matter how much you do to your car? They're definitely on R5 supersoft tires. I could not win a single event with R3 tires. I had to use R4, and even went to R5 for one race.
I've seen it opined that the non-turbo Speedster may be faster. That's what I used, with max NA power on most of the events, but not all. I bought every option you can get for my Speedster, including all the lightening options and the Increase Rididity option. The only thing I didn't add was a wing.
I also tweaked the suspension:
SR 7.7 / 8.5
RH 90 / 95
SB 5 / 7
SR 6 / 7
C 2.5 / 1.5
T 0 / 0
St 4 / 4
Brake Balance 2 / 4
ASM 0 / 0
TCS 3
LSD 7 / 25 / 17
EDIT - Transmission settings: Final drive to 5.500, Autoset to 25, then to 1 and leave it, then adjust the final for each track. You want to redline in sixth at the end of the longest straight on each track.
The LSD settings made a big difference.
Even with all of the above, its still a battle. To me this is one of the best events in the game.
Now that I've got my Calibra, I'll come back to the Speedster race to see how much I can de-tune my car and still win.