F1 engine tokens - new engine design

[andyps]

I've just read this article - http://www.motorsport.com/f1/news/red-bull-encoura... - about new developments Renault are making within the engine department. To me it reads like something very close to a completely new engine design so how does this fit within the restrictions imposed by the development token scheme? As a layman my understanding was that the basic engine design is fixed but modifications can be made to certain components. If it is only components being changed why go back to a single cylinder?

I would be interested in any knowledge anyone has.