For the 2.5, after u installed the Intercooler, you will notice turbo lag instantly. Had a few member doing that, but then they're ok with that with the help of tuning chip which gives responsive throttle and power, not to mention turbo kicks in smoother and faster too.
Piping wise, too big is not good, too small is real bad.
Fan below the intercooler is not necessary i guess? Most of the people fit their BOV right before the throttle body, so far only HKS SSQV3D/SSQV4D performs the best. Better get a genuine ones

(Which require to tap wires from the solenoid to the TPS sensor, this type of BOV is activated through TPS)
Besides, there are some fake HKS SSQV3D/4D around which are using fake HKS bov and some china/taiwan made solenoid valve.
VNT to fit on the 2.5? Good luck.

Thais 2kdftv is fitted with vnt producing 142hp so it is doable. Any suggestion on where to get vnt turbo or which company made it?