A great many plot problems that show up in unpublished manuscripts can be resolved with a single strategy. Know what the chase is, and cut to it. Do not write hundreds of pages without knowing the story you really want to tell. Do not write hundreds of pages explaining why you want to tell the story you are about to tell, why the characters are living the way they are when the story begins, or what past events made the characters into people who would have loved that story. Write hundreds of pages of the story, or else you'll find that what you write will not be shelved in the libraries of the future but will instead form the landfill upon which those libraries are built.