What is the song from left 4 dead 2 commercial

The song from the Left 4 Dead 2 TV Spot is "Electric Worry" by "Clutch". I'm assuming the lyrics you heard were:

"Bang, bang, bang, bang! Vamanos, vamanos! Bang, bang, bang! Vamanos, vamanos!"

Don't worry, the rest of the song has other lyrics, not just those repeated words.