At Reddishpink we tend to keep a close eye on the changing algorithms that Google uses to qualify a site for high page ranking. One tool we always standby is Google Page Insights for a 30000 foot overview of what is going on with your site, what stop gaps you may have and potential improvement areas. But by no means is this tool meant as a panacea to achieve high ranking pages.
Have a read at this article for a good run through of where Google Page Insights tests can be useful, possibly impactful and… where it should be a lamp post only. Good to lean, not much light.
And as always contact us for more information on how we can help you with page rankings