The Astmoor trap fells almost like cheating! I almost went crazy trying to find one, until someone mentioned it. I normally don't modify or tune my cars, but I had swapped the engine on my Mercedes truck , just because the stock one has an incorrect sound. That is more than enough to reach 140+ mph in Astmoor.
I managed to do the three street races in Expert. So long as you go for ones that don't have tight turns, you'll be fine. And I'm not embarrassed to admit, I used my truck's mass to... "clear" the road from other competitors.