Im expecting an increase in HP and Nm at the rear wheel from my forthcoming upgrade over stock items:
tuned length twin manifolds, HKS split dump pumps, dual 2.5" into 3.5" front pipe to mate into my cat-back system
running fresh hiflowed steel wheel turbos, 550cc inj, z32 afm, gtr intake & walbro 305lph external fuel pumps, power-fc
eventually going to do a rebuild, and I expect the exhaust to flow over 500hp:
hks oil pump, n1 water pump, 87mm hks pistons, attkd rods, acl race bearings, arp studs, greddy cams & adjustable gears, hks cam springs
cometic 87 x1.2mm full gasket kit, greddy timing belt kit, 30-row oil cooler, 52mm dual core radiator, air intake kit
throw in the electronics, roll cage, wilwood brake setup & semislicks - she should be a decent track car !