Will an axle back performance exhast with a 4" muffler (Nameless brand) affect the ECU or anything else on a stock 2017 Subaru Legacy 2.5i?

A 4" muffler will make it sound like the rice rocket it is.

Lol, dont you have something better to do? Being factory back to the axle, it won't sound rice, just a mellow rumble when on the gas pedal. IMO, boxer engines sound sweet, but now even a WRX or STI are too quiet from the factory. I have a Legacy, a midsized family sedan. 175hp, AWD, 30mpg and the safest car on the road. That's less rice than an ecoboost Mustang or any $70k European sedan with their computerized exhaust notes.

I guess if you like the sound of a flat 4 or flat 6, go for it. Me? I am into the rumble of classic V-8s and a 4 or 6 banger will never sound as good as a V-8. Also...No, I don't have anything better to do. LOL

Hey Bob. Boxer engine is not a flat 4 FYI.

A flat 4 IS a boxer engine.

Boxer engines are of the "flat" design. Subarus use the Boxer or "flat" engine design. Perhaps some study and reading is required.

Hey Bob ;)