All good ideas. Personally I would put the money into: 11mm injection pump, lift pump in fuel tank, larger injectors/turbo+chip tuning in addition to the supporting mods you mentioned.
You could probably do a dual ECU but I have not personally seen it on TDI. The boost setup on TDI is not exactly the same as on older cars. For one thing, my boost controller on another car is set up to let pressure pass the dual stage solenoid in response to its boost sensor (Blitz id-3). Your car moves the N75 solenoid to let vacuum pass in response to boost. I don't know if a conventional boost controller will work on mk4 and newer TDI due to the setup and vacuum can instead of wastegate other than sending it into limp mode. Not saying it won't work but I don't know how.
ECU tuners can set up the ECU to switch the line between vac and pressure for VNT-nonVNT swaps, they would know the details.
Take a look at this article: http://www.myturbodiesel.com/1000q/a4/VNT-wastegate-adjust.htm for some details on how the VNT can works.
Feel free to talk to kermatdi.com, one of the site sponsors, they have a lot of supporting parts in addition to engine tuning. There are many other places to buy parts and get tuned as well.
You could probably do a dual ECU but I have not personally seen it on TDI. The boost setup on TDI is not exactly the same as on older cars. For one thing, my boost controller on another car is set up to let pressure pass the dual stage solenoid in response to its boost sensor (Blitz id-3). Your car moves the N75 solenoid to let vacuum pass in response to boost. I don't know if a conventional boost controller will work on mk4 and newer TDI due to the setup and vacuum can instead of wastegate other than sending it into limp mode. Not saying it won't work but I don't know how.
ECU tuners can set up the ECU to switch the line between vac and pressure for VNT-nonVNT swaps, they would know the details.
Take a look at this article: http://www.myturbodiesel.com/1000q/a4/VNT-wastegate-adjust.htm for some details on how the VNT can works.
Feel free to talk to kermatdi.com, one of the site sponsors, they have a lot of supporting parts in addition to engine tuning. There are many other places to buy parts and get tuned as well.