Here are some great columns that will teach you a lot about how airplane engines work.
They apply to non-boosted general aviation engines, but the principle is the important thing. (he also has 5 columns on turbos, see full index
http://www.avweb.com/news/pelican/list.html )
Manifold pressure:
http://www.avweb.com/news/pelican/182081-1.html
Propellers:
http://www.avweb.com/news/pelican/182082-1.html
Fuel mixture:
http://www.avweb.com/news/pelican/182084-1.html
They are very well written and extremely informative. Keep in mind they are written for the general aviation community and their flat four 360 cid or flat six 540 cid engines - so he addresses the availability of instruments to them and some "old wive's tales" and misconceptions within that community related to those engines, but the fundamental principles shine through bright and clear.