Have an HKS Hi flow filter kit on my v3 wrx, i read that these have very poor performance in comparison with Apexi and K&N cone style filters. The filter element itself is not old although was very dry, i applied a very light coat of oil to fix this but i've now learned this may affect and possibly damage the MAF sensor. Any pointers?

 

Is this a mushroom filter or a panel?

 

Its a mushroom filter mate, yellow foam. I must admit im tempted to go back to panel filter as its not over 300bhp , and to be honest, and i may get roasted by some people for saying this, but i get the impression some HKS equipment relies purely on the brand name and not overall quality. ?

 

just bought a sti panel filter from roger clark motorsport very good quality at 50 quid

 

David : My experience is that the HKS foam filter will let through quite large particles of grit.
To get any gain from a cone you need to have your AFRs adjusted. ie. remapped.
The pannel filter is adequate at your power level and has a nimber of advantages. Contrary to popular belief, there is not much wrong with the Subaru O/E pannel filter other than it needs changed regularly. 6-12k miles.
I standardise on a K+N pannel if I am keeping the car.
There is virtually no power difference between pannel filters.
I must say that I share your view on some HKS products and it is only by testing items, whether it is an exhaust, turbo or filter, that you start to find out what works, sometimes with surprising results.

 

Many thanks for the advice guys, the wagon has an impeccable service history and low mileage so it would definitely be a shame if she was breathing in dirt and grit for minimal (if any) power gains. Im going to revert back to the good old panel filter. I may even switch the coilovers back as well as i dont think the bumpy ride is doing the MAF sensor any favours!. For sure its always something but then thats part of the charm of ownership i guess.