If there are leaks present, it will spray oil mist out when boosting. Therefor you will se wet area if it’s leaking. So just visually check the entire routing of the air hoses with all its connections (weak point) including inter cooler…

 

You can use fairy liquid and water or kids bubble solutions cover all the hoses an joints rag it and look for areas of bubbles

 

Years ago I added a Shrader valve to an old scrap hose on my 2.5. The test pressure is only 7 psi so I just pumped it up with foot pump. you can wiggle the hoses whilst under pressure. Mine held full pressure overnight so no fault found. I don't think this would work with a big leak since it wouldn't build enough pressure to test in the first place, it's better for elimination purposes. I think I must still have it somewhere if anyone with an old 2.5 needs it.

I did try and make a smoke machine out of a vacuum cleaner (reversed to blow) and a cheap disco smoke machine. I wanted to check for exhaust leaks but I never really got it working properly.

 

Found it.

 

great idea