Categorically False!
A boosted Yugo, Kia, Saturn (except Sky), Hyundai, econo-shitbox will not get you laid.
A boosted car which is one of the following will HELP you get laid.
Somewhat Expensive to Extremely Expensive
Somewhat Unique
Sexy
BUT, what will get you laid is a good wingman, a puppy, or cute small child, and at least some game.
And THIS combination is guaranteed to get you a threesome:
http://i247.photobucket.com/albums/gg127/jerome6969/tilleyandsam.jpg