Im now the happy owner of a pre-owned piston dump valve ( Bailey one ). I can see the big T piece fits between the intercooler and the engine but there is a small bore tube from the top of the dump valve, Im not sure where this should go.
Assuming that it's a c20let and there's an Amal valve fitted there'l be two vacum lines coming from the turbo and one from the actuator, the one from the actuator and one from the turbo go to the amal valve, it's the other one you want. It connects to a small plate on the turbo (4 x allen key bolts), once that plates off you need really to put something in there to keep the inner valve closed and do the plate back up, a washer won't be big enough, probly needs to be 3mm thick. Block the hole aswell to be on the safe side. The vacum pipe that went in there then goes to the top of the dumpvalve. I ain't got a scanner or I could post the instructions that came with mine, sure someone could though ?