Can you get a car tuned very well using datalogs alone?

 

It depends a lot on the particular setup and its complexity. Most issues can be addressed through the use of datalogs only, others won't be as easy. And since I mentioned easy, it is a lot easier and less time taking to do the tuning in person while driving the car than trying to figure out the issues from looking at logs and reading someone else's experience.

 

Depends on if all the sensors are workign properly..

If you got a car with a bunch of codes, malfunctioning sensors, exhaust leaks, vaccum leaks, etc.. it will be impossible to tune the car.

You can't really tune over mechanical problems.