So I'm looking at a GTR and like most people, I want more power eventually.

A guy who did my port and polish on my turbo/turbofold on my SRT said he can do anything to the stock turbos. Big wheel, billet, steel, whatever I need (he's heard the horror stories of ceramic turbines). He rebuilds Stage 3 Mopar SRT turbos that generally produce 325-350hp and turns them into 650whp+ monsters, so he can handle this! Makes his own wheels too.

My question is, I know 1bar is generally considered the max for the ceramic wheels. What is the turbos max effeciency range? Are we talking 1.2? 1.4? Assuming everything is brought up to the strength to handle these pressures. When are we looking at this turbo running out of steam and just blowing hot air?

Probably not much above that. Pull up the turbo compressor map and post it. That will tell you.

What is the turbos max effeciency range? Are we talking 1.2? 1.4? Assuming everything is brought up to the strength to handle these pressures.

Never mind the max efficiency range, if you boost over .9 bar on stock R32 ceramics, you'll overspin the exhaust-side wheel and disintegrate it.