Is it safe or ok to have for example 750cc injectors and fuel rail put in without a piggyback computer or reflash? Will that result in a rich condition because more fuel will be delivered?

 

I'm not sure how it could not result in a rich condition.

 

yes....that will definitely run a lot richer....I wouldn't recommend driving around with it too much without tuning, you'll just foul up the spark plugs.

 

Isn't the EVO already running rich? It's drowning time...

 

yup

 

Your fuel management will be changed in that the injector duty cycle will be lessened for a given flow rate. The O2 sensor will still operate fine to control the a/f in the closed loop but you may experience idle difficulties.

 

Car will run at part throttle cause the ecu uses the 02 sensors to adj the fuel. But once you go past about 60% throttle the ecu stops reading the o2 sensor and goes off a base map that has fuel settings set permantaly. Which will cause your car to run very rich and break up once in boost from being to rich.