Oil in turbo compressor housing, oily residue intake tube, and in intake manifold
 

I just started to install a 60mm turbo housing and wheel and also injectors. When I pulled the intake tube and turbo compressor housing apart I noticed a little residue on the turbo housing and inside the intake tube. And also a good amount of oily build up inside the intake manifold.
Any ideas on where to start?
is the turbo seal bad?
It's an off road truck that I haven't driven enough to notice excessive oil use.
any help would be much appreciated