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GFB have re-designed their WRX lightweight pulley to provide even more benefits. It is now shaped to look exactly like the factory Subaru pulley, so it goes unnoticed in your engine bay - it even uses the factory belts! A significant amount of weight has been removed from around the rim for even better throttle response. The pulley weighs in at 578g (previously 790g), compared to the factory 2180g on the WRX and 2575g on the STI. This pulley will improve throttle response (particularly off-boost response) and allow the engine to rev more freely in the upper rev range.

It suits all Subaru EJ-series engines, and does not require additional belts

Featuring GFB’s patented venting bias adjustment system, the Respons allows you to precisely control how much air vents from each of the two outlets.

Why is this so important? Two key reasons:

Adjust how loud the blow-off sound is. Recirculate all of the air for silent factory operation, vent it all to atmosphere for maximum noise, or set it ANYWHERE in between to suit your preference.

Get a blow-off sound WITHOUT causing stalling, backfiring, or any other BOV-related issues, even on a car with a sensitive airflow meter (MAF).
Hold on, it gets better. The Respons isn’t just a noise-maker. It also;

• Offers better throttle response
• Faster boost recovery on gearshift
• Unlimited boost-holding!

For example, using GFB’s TMS (Turbo Management System) principle, tests show that the Respons can return the engine to peak boost up to 30% faster than a factory diverter valve when shifting gears.