The communication from Kudos was head and shoulders above and they were quicker for parts ex-Japan compared to Amayama.
The pricing from Amayama was better for some items so I would check with both but when it takes longer to arrive than expected and they ignore your emails you have to consider that aspect.
He has been given legit answers.
By your own admission the Ebay special is worse than a decent turbo. Pretty much what every is telling the OP.
There are few success stories for Holset on SAU because they are a worse option that what he is being suggested.
Can lead a horse to water but holding his head under and making him drink is hard work.
I would buy a decent standalone.
Having modified Nissans over several years I always wish I had listened to those that were more knowledgeable and bought quality parts in the first place whether it was injectors or ecu's or tyres. It seems like you are saving money but the cost comes when you get a poor result and/or do it all over again.
Everyone here is recommending you ditch the EMU and go a standalone as you will get a better result. Good luck which ever way you go.
Instead of looking for why the EMU is crap on WWW try looking for information on why people choose high quality stand alone ECU's. Why would there be much information on a path that most choose to avoid?
The cost of doing things twice hurts but if you have your mind made up then good luck and I hope it works out.
There is a fair bit more trimming on radiators that are thicker than 42mm from memory. So I would choose one this size or thinner if you want to refit the shroud easily.