Your advice please

[306 Turbo]

Hi guys hope you can help?

I have a peugeot 306 with a 8v turbo lump fitted which was done by Ecosse.

I have started to notice black soot on the back of the car and all the piston's have oil on them when i removed the plugs.

The engine has adjustable boost between 5 and 15 psi and is running JE piston's.

From searching you site i'm thinking it's the turbo oil seals but just wanted your thoughts.

Have done a compression test and thats ok.