just built motor... has 500 miles on it... it runs strong compresses 200 all the way across... ls vtec stock pistons with b16 head... has ran fine and all of a sudden tonight i come up to a light.. and it dies....it starts right up..and runs fine until i let off the gas... then it dies once it idles down.... no noises it runs fine as long as i have the gas down.... possible vaccumm leak or something

 

Did you recently disconnect the battery? The ECU would need to relearn the idle.