Just search my username on youtube- TheChosenOne 87!

There is an open place where you should be able to do it, close to the end of the level.

How do you complete (at mission 8) where you must slide 200 feet upside down?

Okej! I got it now! Use your super boost! Turn your car upwards from were you start until you see a tall bulding. Follow it to the top and you will see what looks like oblong pillar on the roof. Go behind it and you will also notice fire barrels coming out of nowhere. Follow it down you will notice one-two zombies standing on a pillar with two ways to take, right or left. Take to the right and before you go down there be sure to press that boost button and it take some time to regulate the car's directions to get to 150.

How?