I get the no-budget thing.
There will be a spot you can find with trial and error that will generally work for you. Your low end performance will suck, you'll have the equivalent of a cork in your exhaust at higher RPM but it will "work". The turbo may not last as long, but it will "work".
The yellow line in this graph is the vane position during a drive on my VNT (0=fully open, 100=fully closed) - there isn't really a 'sweet spot'. "Cruising" boost is around 4-5 PSI on my setup (graph is in kPa - 100 kPa = 14.7 PSI), depending on RPM that can be the vanes fully closed or it can be the vanes resting around 60%. With the pedal to the floor I'll hit about 30 PSI with the vanes anywhere from 40% to 20% depending on RPM. If I had them set at say "60%" all the time my turbo would explode absolutely 100% for sure. It would be 'safe' to have them at 20% but I'd have very little boost EXCEPT with the pedal to the floor at 4K RPM.
![](https://c4.staticflickr.com/8/7680/17682213005_58b4d8e963_z.jpg)
If you have no budget, then you probably can't afford to replace the turbo if you blow it up during your trial and error period. So
SELL it and use the proceeds to buy a wastegate turbo. You should come out about even, but have something that will last a long long long time.
You can also try building a mechanical VNT control system, there's a few versions lurking in the forum. That isn't particularly expensive, just time consuming.