Wow! 900hp..
OK, first things first..dump all the high HP mods. too much HP reinforces the drive fast turn later scenario. The absoulte key to these races are staying off the walls. I'm guessing that since you've already loaded the HP up, you've also set added the other suspension mods?
Turn ASM to 3, and TCS to 1. If you're running in the 400hp range you should be in better control. What type of tires are you running? Try T5 tires. I'm guessing that on a straight stretch, you blast by the AI like nothing, right? So they are beating you in the corners. You need to learn how to lighten up on the throttle when you turn. This is a mantra recited by many people here "Slow in. Fast out."
It works.
What may also be the problem, is that you are getting too nervous, and miscalculating. Relax a bit, and breathe. I found that I tense up and have to remind myself to breathe, when the race is really tight. Turn in sooner than you think, and at a speed slower than you think, Get back on teh gas smoothly. No punching it out of the corners.
Hopefully this will help out a bit. Post up the settings you are using on teh car, and we'll give you some pointers.
Welcome aboard. Glad to have you.
AO