I have heard from a few different people now claiming that adding mods to an Evo with the factory brain will not increase any HP and in fact descrease HP. Is this true?

 

Oops, looks like you missed the Evo forum and landed in Lancer General. Moving to Evo General, you should get more responses there.

But to make a comment, I don't see how that can be 100% true. An intake brings more air into the engine, in which case the MAS adjusts and adds a little fuel, and the combination of the two gets a little more power. Maybe SOME mods will lose power, but others would still be beneficial without a modded ecu (although the gains would be greater with the upgraded ecu)

 

This is not entirely correct. Certain mods, like air intakes add very few horsepower. A few even lose hp. But adding an exhaust can gain you between 10-20 hp, depending on the set-up.

 

Interesting... thanks for the feedback.