Hi there....
If you're only using it for WMI,then the HPA or IE manifold is perfect.
If you're planning a 500+bhp system with port injectors,then you would need something like the Boulekos(the one I have) or the HEP manifold,both of which can use port injectors in combination with the stock DI system.
If you do use a sequential WMI system,then the Aquamist is the best,otherwise systems such as AEM are good value.
The HPA manifold is for a single point injector as far as I can remember,where the IE manifold will accept multiple injectors for a sequential system.
For any of these,you would need the runner flaps removed,and then need RFD specific mapping to avoid cold start/idle issues.