RE: air in fuel lines
There are a number of things that people add to their fuel to kill the foaming. Some fuels already contain them. Check the advertising.
One thing we ought to keep in mind when adding something to our fuel, is what might it contain?
WD40 has been mentioned. It's is somewhat similar to fuel or fuel components. And it probably contains nothing that would upset the combustion. And everything in it probably either burns or lubricates. But some things might contain substances that you wouldn't actually want in an engine. Think about what you're adding and what it's probably got in it.