lightening and balancing along wont really show any increase in power, just far more responsive, but it is partly what needed if your going to make a high reving engine.
But..... i thought an engine has peek point at which its working at its best, this would be a given speed of the piston (Hench why the williams produces power at lower revs, because roughly speaking a williams running at 3k for example will have its pistons traveling at a faster speed then the de-stroked 1800 doing the same RPM, therefore its not as simple as upping the rev limit unless your engine isgot a very wide bore, A better solution would be making the 1800 flow better it the current rev range?
this is all just my ideas and not a proven theory, BenR will have an infinitly better idea what the best route would be.
BenHs made 172 BHP with hotter cams & porting and polishing, and the car (i believe) is still very driveable and idles smoothly, this is the sort of spec i would go for, 172BHP is aot in a little clio!
Also what is to be gained with the supersprint manifold? i thought the cast 16v and williams tubular were OK any way, The 16v being slightly more restrictive but therefore better for torque, I would be suprised if super sprint had spent as much time and money on the design as Renault.