The difference is the header/downpipe/intake cam/ mid section/back box and the ECU settings
The normal Primera P11 2.0 comes with 128 hp(130PS)/125 torque the GT version comes with 148 hp (150PS) / 134 torque.
I own a Primera SRi 2.0 which came with 128 hp and 125 torque as standard. However my car now makes 162 hp and 144 torque by adding GT primera mid section/intake cam/mid section/ performance back box/ k and n panel filter and a Hot Shot Header and downpipe

It can also run 15.8 1/4 miles with 2.1 60 ft times.
