Thanks Richard, had a 1700 tuned xflow Caterham which had 32mm chokes & it drive good. Better than it did with the bored out chokes car came with. I have machined out the spare 30mm chokes to 31.85mm, in process of putting carbs i just serviced back on car, so will try them out, if no better or hopefully no worse i can just fit the other 30mm set.