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18 reviews


I5 Cast Inlet Plenum [Mk2 Focus RS/ST]

mountune's highly-skilled engineers identified an obvious performance and aesthetical improvement to all I5 engines through the creation of an I5 cast inlet plenum.

Extensive in-house CAD and CFD work (by the same team responsible for producing mountune's BTCC, WTCC, WRC and Rallycross inlets) allowed an improvement to be made - particularly around the port entrance to each inlet, as well as to increase the volume of the plenum itself to a more appropriate size for the 2.5-litre engine.

The mountune I5 cast inlet plenum has fast become the market-leader in the I5 cast inlet plenum sector with good reason; proven performance benefits across a multitude of power outputs, durable construction, OE packaging for ease of installation on mk2 Focus RS, mk2 Focus ST and various Volvo models - all combined with the assurance of buying from the best in the business and a name you can trust.

The I5 cast inlet plenum is supplied in an "RS500" black, and comes supplied with the required hardware for installation. Fitting takes less than 30 minutes on a mk2 Focus RS and approximately 60 minutes on a mk2 Focus ST (recommended removal of OE induction assembly).

Output improvements will vary on non-mountune upgraded vehicles, dependent on specification of tune, calibration and boost level being run.

Customer Reviews
4.9 Based on 18 Reviews
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    United Kingdom United Kingdom

    Good info quick delivery

    United Kingdom United Kingdom
    Inlet plenum

    Well made bit of kit, looking forward to fitting

    United Kingdom United Kingdom
    Mountune inlet

    Easy purchase and quick delivery This intake fits better with the standard air box unlike the Airtec one I had altho the casting and over all finish wasn’t the best. It’s not perfectly straight along the top edge either.

    mountune I5 Cast Inlet Plenum [Mk2 Focus RS/ST] Reviewmountune I5 Cast Inlet Plenum [Mk2 Focus RS/ST] Review

    Thanks for the feedback John. There will always be small marks like this when you use gravity fed casting due to that particular process but in part is also why we offer a painted version for those that want a perfect finish. If you'd like to discuss this further, please get in touch at and we'd be happy to look at your options.