yeh 200hp isn't a whole lot for 2 litres of 2 stroke, even the standard 500cc road bikes mad 135 odd hp and the moto gps well over 200hp. seems weird it doesn't have expansion chambers, most 2 strokes barely make power at all til they hit powerband.
20g's is a pretty standard build really but if that was my limit i would spend say 6g's on a hayabusa motor, 4g's on a winters quick change diff, say 3g's for parts like the tailshaft etc. and say 2g's for all new suspension arms fully rose jointed and all that. then say 2g's for interior parts such as seats, steering wheel pedal box etc. then about a grand to get it painted. the remaining 2g's will quickly get spent on minor things. this still leaves you to do all the work apart from the actual spraying of the car.