Help with Nissan D21 1987

Hello friends, I apologize I need help with some manual, I have a Nissan D21, 1987 model, from the USA.

Bring a Z24 engine, it is 4 cylinders with 8 spark plugs and double coil.

It has an injected carburetor that already gives me a headache, it consumes a lot of gasoline and not found mechanical that makes entry.

I would also like to increase the power to the engine, but I don't know if that engine can be modified, if anyone knows anything about this truck, they are appreciated in advance