The fuel injection is calibrated for the diameter of the throttle body, not the size of the engine - changes to the intake and exhaust will affect the fuel injection, but it will have to be hooked up to a dyno and re-calibrated by an experienced tuner with a program compatible to the electronics.
Boring the engine will give a bit more low end grunt and revamping the variator will change the engagement characteristic, but you will need to get a high lift cam to get back some of the top end you lose when you increase the bore. Likewise the stroker crank will boost the low end grunt wile lowering the redline RPM limit.
Have fun - engine building is great if you have the time and money - if you have the time, you might get it all done in a 2 to 4 week to month time frame. If you are going for maximum performance allow about 6 months to a year for disassembly, machining, clearance checking, head porting, recutting the valve seats for the larger valves, checking the clearance between the piston and the valves and the overlap clearance between the intake and exhaust valve (one is opening as the other is closing and they have to miss), finding an over sized exhaust system to match the enlarged exhaust port, final assembly and the dyno runs to fine tune the EFI.
Now get the variator tuned for the performance curve of the engine, possibly consider a heavy duty driven clutch assembly and a heavy duty belt.
Whew! I think I would just consider a Chinese 250 instead of all the work of building a Chinese 150 into a 160+, but on the other hand, if you have free time, go for it and let us know how it progresses
