Can consider the DIY section, but would it be one DIY section for all different categories? or each section got a DIY subsection?

I think for now just put a DIY on the subject title then post it under the relevant forum? (Eg. engine, ICE, suspension)

What u guys think?

That will be good, But must make sure it comes with pictures. Can make it compulsory.

and have a few knowledge base pinned post as well inside the DIY section.

Added a DIY forum:
http://forum.lancerzone.com/index.php?showforum=35