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Hi there, I wanted to know if there are any real gains in replacing the manufacturers air filter with a performance one? I aslo have concerns on its effectiveness to perform its core functions of actually filtering the junk out. Is there a trade off between performance and engine maintenance with performance air filters?

You need to be very careful fitting aftermarket or non approved performance parts full stop, but airfilters are a definite potential problem.

Subaru's have been one of the most popular cars to tweak in terms of performance in recent years and we have seen firsthand, the results of changing the air induction system including airfilters.

As you say, the job of the airfilter is to filter the air and to, amongst other things, allow the correct information to be feed onto the on-board management computer. This in turn allows for the correct air/fuel ratio to be delivered for a certain engine condition.

In a worst case scenario an engine can start to run very lean because over time, a film can form over the air flow sensor almost tricking the computer into believing the engine needs to be leaned out.

The end result when that happens can be melted pistons especially after a long and hard drive.

I struggle to believe fitting such an airfilter on its own, is going to provide much improvement in overall performance anyway.

Be careful, for sure manufactures always build comfort levels into their vehicles at time of design and production, airfilters included. Just how far you can step outside the 'safe' boundaries is anyone’s guess however as not every aftermarket part is the same.

Thanks, that's just what I needed to hear. I was never completely convinced about its reliability. It sounds like the same old mantra that if you're going to change one thing you're inevitably going to have to change something else. Every one knows about the guy who squeezed out the extra horse power without changing the brakes. :)