U.S. Marine Staff Sgt. Liam Dwyer lost his left leg in Afghanistan three years ago when he stepped on a land mine. He was forced to undergo surgery every other day for five weeks to prevent infection. After that, more surgery to reconstruct his life. ONce cleared, Sgt. Dwyer began a racing career that wound up in a Street Tuner victory in the Continental Tire Sports Car Challenge last weekend at Lime Rock. The win came with co-driver Tom Long but Dwyer is the hero in this story. Listen…