Another thing to check are the short lengths of rubber hose that connect the steel lines and electric pump. I'm helping on an old Ford pickup that had intermittant fuel starvation. Couldn't figure it out until I was crawling under the pickup and started squeezing the rubber lines. Some of them were soft like they were made out of plastic wrap. Any suction pulled them closed. They were not only old but probably not compatible with alcohool in today's gas. A couple feet of 3/8" fuel line fixed the problem.