I got 1000 points on Burnout on 360, I'll try and help. My tag is DC ARENA if you want to look at my list for the game.
The White Mountain Burning Lap is a very tough event, but its not impossible. I presume you're using the various shortcuts on the track? The most important thing to remember is to boost all the time, evening through corners and don't ever, ever crash.
- There are two right at the start (after the forked bridge). Use both of these.
- For the entire lap keep your finger pressed down on the boost, don't ever let up. If you permanently drive on the wrong side of the road your boost guage will stay maxed out.
- Later in the stage there is a little town you drive through, with two routes. On the 2nd route (the easier one to get to without crahsing) has a fork in the road which takes you either side of the clocktower building. Take the RIGHT side route and evade any traffic in that section. There are a couple of walls that stick out along here but you should be good.
- Drive up the set of stairs and make your way up the winding road. Drift every corner and try out stay out of the dirt as much as possible.
- You'll soon arrive at the tunnel where there is the dirt road to the left. Take this short cut.
- After a while the dirt road splits and to the left is another dirt road. DON'T take that one, its way too risky and you'll be hitting restart before you know it. So continue along the main dirt road and you'll then get back onto the main road in the tunnel. You should just miss the roof of the tunnel (its quite low).
- From here its just a couple of corners left. Remember to drift everything (tapping brake button), and always hold Boost down.
I had about a 1/2 second left when I did it. I reckon that one, along with the final Burning Lap (Indy racecar around Motor City) are the games hardest events. I really struggled with the final BL on Xbox, but on Xbox 360 they have adjusted the time slightly (and made most of the other BL's harder as they were too easy on Xbox).
Hope this helps.
