There are a lot more cost effective means to making more power. BIG turbos are where the BIG power is going to be. The results from going from a 3.0L to 3.2L or 3.3L just isn't going to be worth the costs involved.
"I'm not surprised you get along well with all the other neighbours. If you put fifty children with Down's syndrome in a room there is going to be a lot of hugging." David Thorne