GSX-S Airbox restrictor plate
Under the air filter is an GSX-S Airbox restrictor plate with a hole about 25% the size of the GSXS air filter, this seems to be designed to reduce noise emissions and can easily be removed to improve performance. Removing this seems to add to the airflow and reduce the torque drop at around 5000RPM as well as improving the induction noise. I also fitted a BMC GSXS air Filter
BMC GSXS Air Filter
BMC air filters are produced using a “Full Moulding” system that enables the characteristic red filter to be realized from a single mould with no welded joints thus avoiding easy breakage. The rubber used in BMC air filtering systems has a long life, is very durable and has optimum adhesion characteristics to all shapes of airboxes.
BMC filters are made of a multi-layered cotton gauze soaked with low viscosity oil covered with an epoxy coated alloy mesh to ensure protection from petrol fumes and oxidization due to air humidity.
All BMC air filters are pre-oiled.
We strongly advise regenerating the BMC GSXS Air filter using the original BMC washing Kit; the kit contains detergent and oil dispenser (spray or with batcher).
We advise regeneration every 15000 km to guarantee long lasting performance and duration. This value can change based on the environmental conditions the car is used in (e.g. non tarred roads, presence of pollen, dust,…).
The stages for correct filter washing and oiling are specifically indicated in instructions inside the pack.