Does anyone know if the scorpion tuner 5 back box for sale in the for sale section will fit an 05 sti and what do they sound like are they loud or not too bad.
And will it improve performance

 

I cant tell you about fitments I am afraid.

But sound wise from previous scorpion back boxes fitted they do give quite a nice deeper sound, but, not too loud either.

Performance wise, maybe a slight increase, certainly not noticeable, although the additional noise may lead you to think its a more sporting drive