Just thought id post how i got the Perseverance Ach for people like Mr.Aim who are struggling to get it.
I went into a race in Flatout mode and i didnt know if i had to finish the race or not, so i just restarted after i crossed the START line 7 times in a row, no achievement. So i thought, ok ill just complete the race then restart. I did the race twice and i came 10th then 8th as i was concentrating on getting Heavy Blast and others, then on the 2nd and final lap of my 3rd race, i was clear in 4th place on my own about halfway through the lap and it just popped up Achievement Unlocked - Perseverance - 10G. Seemed a bit odd to me but im not complaining.
Also i found a REALLY easy way to get the Heavy Blaster Ach, do a bonus race, the first one, figure of 8. The at the start, trail behind the other cars a bit, when they go straight through at the cross in the 8, you go left, the wrong way, when they come around the corner they should be boosting right at you, if you boost and hit someone head on... Achievement Unlocked.