Replacing foot valve will not increase pressure, it will only hold pressure steady while pump is off and all fixtures are closed. The reason I say jet assemblys can be a pain, is because they have jets in them that can clogg, or wear out(not often) and when this happens, its hard to tell for sure if it's a pump problem or a jet problem. Jet assemblys must be sized exactly to pump, so if you replace the pump, you have to replace the jet assembly, unless you get the same spec pump that you had, and then if it doesn't work you have to pull jet assembly anyway and fix or replace it. I may be talking a little out my arse, because I've only worked on these things a few times, but I had a fight with them every time. Hope someone else can give you some better advice. If not, I would look into replacing the whole works.
