Alright, I figured why I was so far behind.. the Bob was too low level.. I've found the loctite NSX a devastating car, simply for its sheer power, along with impressive downforce.. it seemes like the Bob don't like it on cold tires unless I'm running full downforce, but does still shatter the opponents, even without coaching. My Bob went to first within 5th lap depending on the opponents, and exits the pit before the 2nd place are even in sight.
The strategy:
I rarely go for turbo upgrades unless I don't reach 600pp without it. I go for full DF, throw in about 100kg ballast and reduce power until you hit 600pp.
At the very start of the race, tell him to pick up the pace. He'll pass one or two on the straight, and keep fighting up the pack. If there's a gap between packs, pace up now and then to keep him from going cold. If he has the lead by lap 7, let him pit on lap 7-8 depending on his speed ( his level determines his speed, ergo sometimes he will finish lap 7 before he wants to pit). But if he dosen't lead by pit time, skip the pits and go the full race without pit stop. The tires will wear thin, but the others don't have the speed to catch up before its too late.
Any NSX does the trick, but I found the loctite one the most stable, and overall best for Bob