Intake - exhaust = breathing formula?



How about the engines need for back pressure (not sure if that is the correct word here, since english is not my native language) in the exhaust system, when increasing the intake?

If one, for example, open up the end can diameter a bit for more "exhale", and also modifiy the intake to get more air/fuel into the combustion chamber, will this affect the balance as much as decreasing the power in lower register or is it negligible in the context for a 4 stroke bike engine?

I´m thinking of...

Intake - exhaust = breathing formula?