Jets, Filters N Zorsts

Sorry if this has been done before, but I understand to a degree about jets, air filters, exhausts etc However, I'm a long way off being any kind fuelling expert. So if anyone out there has a great knowledge store... please feel encouraged to enlighten me!

If you change filters or exhausts, you change the flow of the fuelling, sometimes you need to alter jetting or ignition programming etc. But what affects what? What are the symptoms of poor fueling so you know how to compensate? Time was oily plugs meant too rich a mix etc

I'm quite happy to read a book if pointed in the right direction, or a reliable website... I just wanna get a firm handle on basic bike tuning.