I recently purchased a R33 with a "FREDDY" FFP already installed. While the car already makes decent power with other power supporting mods, it wouldn't be my first manifold choice if I was doing the build my own way.
I love the RB26 plenum and I think if I end up changing my current setup I'll be looking at doing this conversion with the RB26 adaptor plate. I'm just waiting for VCT solenoid relocation kits to be released from Otaku Garage which look somewhat promising.
On the other hand, my fiancé's R34 makes close to 350kw using a stock intake manifold on her setup. Current limiting factor at this stage is her Blitz return flow intercooler.