I can't offer much of an opinion on which ECU to use, because I don't have any experience there, I have always just used piggybacks on a factory system.
Turbos however, the hardest thing is to try and match the boost level with the performance curve and the engine capacity. A 1.9 petrol engine that makes peak torque near 3000 stock and peak power at 4500 will likely use one of the modern diesel turbos very well, but they use a lot of boost generally, so you may have to tame it down a bit.
This website is just the best thing in the world for this type of matching. It has heaps of compressor maps, and you can change engine characteristics for the real world and get a repeatable output.
http://www.squirrelpf.com/turbocalc/
I used a 1.9L motor, with target HP pk of 175 @ 5000, TQ pk @ 3500, redline @ 5500, BSFC of 0.5, and pressure reference of 14.0:1. I didn't use an intercooler, so no losses (that's a personal thing, I would use a 2-stage spray instead).
When I plugged in the turbo map from a K03-2072, which is very very close to the K-series turbos used on both the 1.6L Citroen HDi I used to have and also the 1.9L TDi VW, the map suited it beautifully.
Have fun.
😁
