Torque
 

Been reading some things and lots of people say the 2.5 has a lot more torque than the 2.0. I'm getting a jdm 2.0 2006 sti which I'm assuming is a twinscroll? If so what difference will the twinscroll make? More torque?

For a start it won't blow itself to pieces!

The 2.5's will always out torque a 2.0 on a like for like basis but the twin scroll has a very quick turbo response (less lag) and a more linear power delivery I believe. But you do lose the Subaru burble.