I have the Forge one in the picture you have linked above.
My mate has the APR one on the picture you linked above (albeit it on a Leon Cupra Mk2 240PS).
Dump Valve (DV)
Diverter Valve (DV)
Blow of Valve (BOV)
By pass valve
are all flavours of the same thing. Essentially they are all valves used to hold pressure in the system up to a point regulated by the ECU (usually between 11-16psi on standard cars, and anything upto 24psi on remapped cars).
Where you are right in saying some are located near the turbo, others are located round the front of the engine.
The reason for this is that VAG group have had multiple revisions on DV's as diaphragms have been splitting and internals have been ceasing. When the DV was located on the Mk4 Golf VAG platforms, the DV was mounted on the TIP (the OE one had a habit of collapsing under high temp/hard usage). Also the turbo was so close to the DV, it was deemed that this was affecting the reliability of the DV.
Hence tuners started to cold side relocate the DV's with a long converter pipe to the front of the engine (
link) to reduce the temps the DV was exposed to. Supposedly this enhanced performance and lifespan of the DV, whilst sharpening throttle response.
So what did VAG go and do on the Mk5 Golf??? Mount the OE DV right near the turbo
. Well f**king done
. So again the problems kick off with the DV's overheating / failing and multiple revisions. When they came to making the new S3, TT-R, Leon Cupra Mk2, and Golf Ed30 someone at the VW engine division had the bright idea of putting the DV frontside of the engine
. At last!!!
So hence the earlier cars DV's are located a the back near the turbo, whereas the new cars are mounted at the front by the fuel pump. Both are the same beast.
The only other component that sits on or near the turbo on earlier cars is the actuator valve (
link), and not many 'non serious' petrol heads use these as it is playing with fire in the wrong hands. The are supposed to increase OE boost pressure if you adjust the tension on the actuator spring, but I wouldn't fancy it much. Don't know much about these myself so I bow to someone elses knowledge if they can help out here. (Hopefully Devon Mikey Boy will read this....)