Reddit mentions of K&N Engine Air Filter: High Performance, Premium, Washable, Replacement Filter: 2003-2019 Subaru H4/H6 1.5/2.0/2.5/3.6L (Forester, Legacy, Outback, Impreza, WRX, Levorg, Crosstrek, Tribeca), 33-2304

K&N drop in thats dry. Just take it out to clean once in a while

Here's my comprehensive list of what I have added to my 2018 WRX so far:

• OEM Crystal Black Silica Touchup Paint
  J361SAJ000A1 - T/U PAINT CRYSTAL BLACK S - Subaru
  https://www.ebay.com/itm/253360200768
  
• OEM Wind Deflector (9/17/2018)
  Subaru Genuine E3610FJ860 Side Window Deflectors, 1 Pack
  https://www.amazon.com/gp/product/B00U0FG7IE/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1
  
• Rear Bumper Applique (9/17/2018)
  Genuine Subaru E771SFJ600 Rear Bumper Applique, 1 Packhttps://www.amazon.com/gp/product/B0089E4Q72/ref=od_aui_detailpages00?ie=UTF8&psc=1
  
• High Beam/DRL LED headlight bulbs (9/12/2018)
  Auxbeam 9005 LED Headlights F-S2 Series with 2Pcs 9005 HB3 H10 9145 LED Headlight Bulbs Conversion Kits 72W 8000LM Bridgelux COB Chips Fog Light
  https://www.amazon.com/gp/product/B01KFBPAJO?pf_rd_p=d1f45e03-8b73-4c9a-9beb-4819111bef9a&pf_rd_r=5B9ETM0YME2Q0RAZW9PK&th=1
  
• Cobb AP with MAP 91/93oct Tunes (9/6/2018)
  COBB TUNING ACCESSPORT V3 | 2015-2018 SUBARU WRX/STI (AP3-SUB-004)
  https://www.maperformance.com/products/cobb-tuning-accessport-v3-2015-2018-subaru-wrx-sti-ap3-sub-004
  
• Low Beam LED headlight bulb (9/4/2018)
  H11/H8/H9 LED Headlight Bulbs Conversion Kit, DOT Approved, SEALIGHT S1 Series 12x CSP Chips Low Beam/Fog Light Bulb- 6000LM 6000K Xenon White
  https://www.amazon.com/gp/product/B079KB7QX3/ref=oh_aui_detailpage_o05_s00?ie=UTF8&psc=1
  
• Smoked Tail Light Overlay (9/1/2018)
  IAG ROCKBLOCKER SMOKE REVERSE LIGHT OVERLAY FILM KIT | 2015-2018 SUBARU WRX/STI SEDAN (IAG-BDY-2015)
  https://www.maperformance.com/products/iag-rockblocker-smoke-reverse-light-overlay-film-kit-2015-2017-subaru-wrx-sti-iag-bdy-2015
  
• Mirrortap Cord for Uniden RD (7/14/2018)
  MIRRORTAP POWER CORDS MirrorTap MTX-1020, RJ-11, 20" Long, Patented Radar Detector Power Cord With 2 Amp In-Line Fuse, Military Grade Taps, Made in USA
  https://www.amazon.com/gp/product/B00L2SVXQO/ref=oh_aui_detailpage_o05_s00?ie=UTF8&psc=1
  
• Mirror Mount for Uniden RD (7/14/2018)
  BlendMount BND-2000R Aluminum Radar Detector Mount for Uniden DFR6/7,LRD950 (EXCEPT R1/R3) - Compatible with Most American and Asian Vehicles - Made in USA - Looks Factory Installed
  https://www.amazon.com/gp/product/B06ZY5FYCC/ref=oh_aui_detailpage_o09_s00?ie=UTF8&psc=1
  
• Alloy wheel touch up paint (7/20/2018)
  Subaru alloy wheel paint WRX 2018 Gray
  http://quiktouch.com/eng/product-detail?subaru-alloy-wheel-paint-wrx-2018-gray&id=6295
  
• Towing Warning Sticker (6/22/2018)
  WRX w/ STi wing AWD Tow Warning Decal Sticker adhesive inside mount
  https://www.ebay.com/itm/201251688281
  
• Fuse Box Coin Container (6/20/2018)
  2015 - 2017 / 2018 WRX / STi JDM Subaru genuine coin box pocket fuse cover lid
  https://www.ebay.com/itm/201597032045
  
• 2x Trunk Cargo Hook (6/20/2018)
  OEM 2017-2018 Subaru Impreza Sedan Trunk Cargo Hook Bag Holder NEW F551SFL100
  https://www.ebay.com/itm/OEM-2017-2018-Subaru-Impreza-Sedan-Trunk-Cargo-Hook-Bag-Holder-NEW-F551SFL100/192483488447?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649
  
• Wheel Lock Kit (7/24/2018)
  Genuine Subaru B321SFG000 Wheel Lock Kit
  https://www.amazon.com/gp/product/B007CLSJRQ/ref=od_aui_detailpages00?ie=UTF8&psc=1
  
• Rear Fog Light (6/11/2018)
  iJDMTOY Smoked Lens 3-In-1 LED Rear Fog Light Assembly Kit (Tail, Brake, Backup Reverse Light) For 2011-up Subaru Impreza WRX STI (with Wire Harness & Mounting Bracket)
  https://www.amazon.com/gp/product/B01GSVLSUA/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
  
• Rear Fog Light Plug & Play Harness (6/11/2018)
  SubieBros Rear Fog Light Plug And Play Harness - Multifunction Style
  http://subiebros.com/subiebros-rear-fog-light-plug-and-play-harness/
  
• LED light replacement (4/30/2018)
  10x White Interior LED Lights Bulb Package Kit For 2015-2017 Subaru WRX STI
  https://www.ebay.com/itm/171646325126
  
• Billetworkz Weighted Shift Knob (4/7/2018)
  Billetworkz Subaru WRX/STI Weighted 500g Gear Shift Knob 6 Speed STI: 2004-Present, WRX: 2015-Present
  https://www.amazon.com/gp/product/B071NJDYTP/ref=oh_aui_detailpage_o01_s00?ie=UTF8&th=1
  
• Perrin Shifter Bushing (3/24/18)
  Perrin 2015 Subaru WRX 5 Speed Stiff Brass Shifter Bushing
  https://www.amazon.com/gp/product/B019D8NQD2/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
  
• Perrin Shifter Stop (2/4/18)
  Perrin Subaru 2015 WRX/10-14 Legacy/Outback/14+ Forester Manual Shifter Stop - Black Anodized
  https://www.amazon.com/dp/B019D8RK5W/ref=cm_sw_r_cp_apa_XoDBAbAT15SH5
  
• Rally Armor Mud flaps (1/21/18)
  Rally Armor 15+ Subaru WRX & STi Sedan Only Red Mud Flap w/ White Logo
  https://www.amazon.com/dp/B00RPKG6QA/ref=cm_sw_r_cp_apa_EqDBAbA5TCHJM
  
• K&N Air Filter (12/24/17)
  K&N 33-2304 High Performance Replacement Air Filter for 2003-2017 Subaru 1.5L/1.6L/2.0L/2.5L/3.0L/3.6L
  https://www.amazon.com/dp/B000COC0GQ/ref=cm_sw_r_cp_apa_IsDBAbS3DT7HK
  
• License Plate Frame (1/8/18)
  Black License Plate Frame, Ohuhu 4 Hole Matte Aluminum 2 PCS Slim License Plate Frames with Screws Caps
  https://www.amazon.com/dp/B01MPYE3SB/ref=cm_sw_r_cp_apa_.tDBAb0S850YB
  
• License Plate Bracket Kit (1/8/18)
  https://www.ebay.com/itm/282594278514