What should the vacuum guage read when idling (hot and cold). Mine was on about -8 psi when warm a couple of days ago which seems nowhere near low enough.

 

I've changed nearly all the small bore hoses recently and am at my wits end as to where else I could have a vacuum leak.

mine is usually around -7vac on my aftermarket boostgauge and -50 (don't know what) on the digital boostgauge of my boostcontroller.

 

to find vacuum/boostleaks in the system you could try this method:

http://home.swipnet.se/e-solutions/Vacuumleak.html

 

be very careful with this though and don't go any higher then 0.7bar...I already blew out 2 gaskets using this method, but apart from that it is the ideal way to find vacuumleaks.