This should give you an idea.
2.0wrx, replaced with 2.5 (AVCS STI heads)
Biggest change is the torque, max was 325lbft @ 5250rpm now peaks at 350 at 4500 and holds 350 until 5500 in fact there is 300lbft plus of torque from 3250rpm! Power wise up by 20BHP but at 3500rpm up by 100BHP!
Oh and did I mention only 1.1 Bar boost currently to keep torque down and protect the std wrx 5 speed box! Turbo was at 1.5bar on the previous map!
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2005 Spec B 6MT - KiDO tuned (~270Bhp)
Custom exhaust - Cosworth filter - Samco Intake - Tints - Bilstein B8/B6 & STI springs - SuperPro ALK - Whiteline positive shift kit, rack mounts, rear adjustable camber bushes, front ARB mounts & strut brace, 20mm rear ARB with AVO mounts, - Hardrace Gearbox and pitch mounts - Prodrive PFF7's - Front Brembos - Kenwood CarPlay - 1/2 carbon grille - STI front splitter