Increase the downforce and use Super Soft tires. Then spread the gearing out slightly for a high top speed on the back straight. That might make it better for your lap times.
Had a go with the Formula GT today. My new record now 4.55,599
All aids off this time exepting ABS on 1. No Skid Recovery, Grip on realistic.
I only adjusted the last gear to 400, no suspension changes.
The F1 cars are lighter than the 787B, with just as much power and probably superior aero. It's amazing the 787B is only off by around 30 seconds over such a huge track.