Okay I finally figured it out. I found a tune and used that...can't remember the link and I'm not sure it was the reason actually but I just thought I'd mention it.
I had the same problem as everyone else, hitting the barrier after the tunnel into the chicane. Bob does that when he's all hot and bothered and you've upped his pace. If you leave him alone at the beginning of the race he'll usually rapidly move into second or third, passing guys on his own. After that, increase his pace heading onto the main straight, but after the esses (or he might dummy himself into that barrier too) and then down pace as you enter the tunnel. Sometimes I doubled down the pace when he got a little hot as I hit hit the crest of the hill for the left hander and then again heading into the tunnel and then back up again on the main straight.
He'll still wipe out once in a while but do this a couple of times and he'll win eventually.
. 2J is a surefire way to win it.
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