I'd suggest looking at this thread:
Note that Y8s has done some dyno testing on VVT showing low end and top end benefits. At the end of the day, the real benefit of VVT is going to depend upon a few key variables:
1. Are you going to get an aftermarket/custom VVT intake cam?
2. Are you going to get an aftermarket/custom exhaust cam?
3. Does your aftermarket ECU support full control of the stock VVT system?
If you really want to maximize the VVT benefit on a "built motor" you are going to have to model (or have a custom cam grinder model) the airflow of your proposed engine combination. This starts to get a bit complicated on a FI motor because you need to supply blower stats in addition to all the other engine stats (induction system CFM flow, bore/stroke, rod ratio, static compression, intake/exhaust valve sizes, intake/exhaust port CFM flow from
.100 to .600, exhaust type, target operating RPM range (1-7K stocker vs. 4K-8K race engine) etc.
I'd suggest doing some software modeling (several good engine sym packages available) to get a better handle before you start spending any money.