The choke mod will make no difference, look at the reduction in size further inside the carby. Anyway heres what we did to a mates stocker. Cleaned up the ports(very minimal porting) and matched the manifold, pod filter, head gasket mod, CDI (not that it makes much difference) exhaust mod(cut out the arrestor) and tuned the carby. Now its not stump pulling power but it made a small difference and it revs a little bit further. A company in America called Powrol sell 15:1 pistons so we are playing with that idea with a cam and bigger carby(and good fuel of course). Back to the mods, you won't notice anything doing one at a time but do them all at once and you'll make a small gain for free basically. And its a good talking point for the boys!