My experience is limited to gasoline engine....but an engine is an air pump....
The more air you pack into the cyliders the more power.
So I have to disagree, air is a bigger part of the power making equatiion.
In naturally aspirated application you need more CI
In force fed apps....add more boost. It is best to use a turbo that is efficent for your application - boost, engine size, operating range. Cooling the air charge is a major help too.
I run 20psi of boost on a street car, with a large air to air intercooler. The injectors are only 100cc larger than stock, backed up with a big fuel pump. The turbo is happy medium between too large and too small...I get quick spool up, but unlike a turbo that is too small, I am not over heating the air. I use a small/simple unit to ajust the fuel via maniuplation of the singnal from air flow meter. My adjustments are based on EGT and 02 sensor voltage..I use a 02 voltage range in place of an A/F ratio, but use an A/f gauge as a quick visual for a safe mix.
She runs like a scalled dog....so my experience = more air = more power