No you can use the turbo how it is, you just have to remove the vacuum solenoid and replace it with a normal boosted wastegate.
In normal operation the VNT turbo lever is in the 'make boost' position when vacuum pulls the level towards the solenoid. As it make boost the vacuum (which comes from an electronic vacuum pump BTW as deisels don't really make vacuum) eases off and the level moves away from the solenoid to divert gases.
Whe you swap it out for a wastegate - The gate will hold the level back at 'make boost' and then when pressure builds up it will move outwards, again diverting gases to control boost.
Pretty much.
Load on the engine is generated in many different ways, Not just through gearing and RPM. For example going up a hill will load your engine much more and help the turbo generate boost, even in 1st or 2nd.
You really just need to do it and find out how it will perform. :dance: