I think you are confused. A turbo with 5 cylindera doesn't mean it's a T5. T5 is a specific thing.

the 2.5T is designed with a low pressure turbo and the torque comes in a lot earlier than the high pressure T5 variants. Is it wise to put an engine in that develops boost so much later in a SUV?

I think I'm correct in saying the 2.3 T5 has a lower compression ratio and slightly different valve timing to enable it to safely handle more boost and more power.

It will probably run but the chances of it running really well are a lottery...

That wasn't my point. My point was the SUV is heavy and needs the power earlier to shift the mass. The T5 power comes in after you rag it.

I'm not disagreeing with you - my point is that difference will probably be made worse by having the wrong ECU.

You should probably stick with a 2.5T engine, as that engine produces instant torque from very low RPM, so is ideal for pulling around the very heavy XC90.

The 2.3 T5 engine, has a lot of turbo lag compared to the 2.5T