The spec C is Subaru’s homologation model which features slight improvements over the standard spec model for racing in the Production World Rally (PWRC) and Group N rally. A minimum number of 1000 cars were needed to satisfy the requirements, so Subaru Technical Institute offered them to the Japanese market.
The big difference between a spec C and other WRXs is a substantial (90 kg) reduction in weight thanks to lighter glass, thinner roof construction and an aluminum trunk lid.
Benefiting the race cars, are new suspension pickups and beefier McPherson strut arrangements with braces to improve rigidity.
Other small details include, power window delete on the rear windows, manual control center of the center differential, larger disc brakes, ball bearing turbochargers, 12L tank for intercooler, transmission oil cooler, Fuel pump with rotating chamber, Air-cooled engine oil cooler, spec C exclusive front/rear stabilizer and a Roof ventilator.
To help increase sales of the spec C, a special RA-R version with a 320 bhp version was released in Nov of 2006.