If that shop claims they can get the same performance as the fp green then go with it. I know that those 1200$ turbo's are not just basic 20g's though. They have larger wheels and compressor housing and all sorts of cool stuff.
To the comment about less efficiency and more lagg. More lagg, yes. Less efficient not necesarrily. How far do you plan to go with your lude? a larger turbo on 7psi will make a good amount more power than a smaller turbo on 7. Everytime I see an 18g dyno I always think no top end. I'm sure it pulls well but I want to feel it puling harder and harder higher in the r's. I'm curious as to what that fp green would do.
seriously though this is not just a standard 20g. and you could sell your 18g and put that toward the cost of the 20g
