hi
i use easy start for diesel engines
on idle i spray it around the pipes and gaskets and again with the revs upted a little and repeat if i find nought at idle
your looking for a change in revs if its leeking its enduced into engine and leak found
take care around the hot parts and always read the safety info on can
another loss of boost not mentioned above is the housing of the turbo where it bolts via 4 nuts and studs to the exhaust manifold its quite common for the housing to crack but you need to remove the turbo and look in this join on the turbo side and see if its cracked this is a classic for boost loss and people try for ages looking for boost leaks but you have tobe sure and put the labour in removing turbo
hope this helps in some way
mark
ps i have had a beer lol