Some questions after PK50XL engine rebuild


I've just finished rebuilding my PK50XL(2?) (V5X3T) engine. I've installed 75DR F1 kit, 3.72 ratio up-gear kit, and new 1616 carburetor.

Questions are:

1. What jet sizes should I use for optimal performance? I will ride about 70% outside the city + 30% city

2. Should I change the exhaust or keep the original?

and finally

3. what's the best timing and spark plug for my setup?