How do different proxies treat headers (refs, etc)?

Question

Browsers

Hello. Interested in subject.
When working with PhantomJS, I found that the analytics sometimes sees traffic sources and keywords, sometimes it doesn’t. It turned out that if the phantom works through a proxy, then in most cases the sources are not visible, but they are needed. Directly everything is fine. Who can say anything about this, who has experience in solving such problems.

Answer 1

referrers are ok, if the proxy is not a web and not a web authorization
is usually active only changes + all sorts of caching ones are added

Answer 2

How to set up - and relate. They can cut, they can change, they can not touch.