a vacuum leak should not cause your truck to quit running.

 

You wouldn't think so but I've seen it. On an '84 Camaro I helped a friend with, when he turned the defrost on it would drop dead, like turning the key off. Worse case it'd let out a massive backfire on its way out. Turned out almost every vacuum line behind the dash to the hvac controls was either broken or just not there at all.

 

I found that with a little throttle it wont die. But if you turn it on while its only idling it dies...sound like a vacuum leak?

 

Yep I'd say definite possibility