2655 vs 2665 engine?

[screamin400]

I know the engine is the same size but wondering if there are any injector pump, injector size or camshaft diff to make the power?

 

[Aaron L]

I'd guess that much of the difference lies in the ECU programing.

 

[screamin400]

I'd guess that much of the difference lies in the ECU programing.

That is what I am thinking. But could be other components.