What do you mean by 'everyone says 32mm carb'. Beware the rumour machine.
A 32, 34 whatever carb will work. My 175 uses a 24. The 250 has stoooopid sized 38mm flatsides(i think). It depends what your after.
Your stock carb will work and set right will give buckets of low to mid range torque/power. The 32 will give you all the big rpm bang, but you will sacrifice lower range power. There will be a sweet spot. The kit makers should be able to help there. It may well be 32.
Generally bigger the carb the peakier the motor, that exhaust will losen a few rpm too, but again losing a little from the lower end.