15+ STi Modification Minimum Recommendations

Common issues to look out for before modification

• Low Compression or Bad Leakdown

In general, you want to minimally have the equivalent of a fully functional stock vehicle BEFORE you start modification.

From there, here are my minimum recommendations based on approximated power goals. Each list is inclusive of the list prior.

Stock Turbo Level 1 (VF ~300whp max)

• Cobb SF or GS Intake
• IAG AOS
• Cobb Accessport

Stock Turbo Level 2 (VF ~330whp max)

• AEM Fuel Pump
• COBB EBCS
• Quality Catted Turboback Exhaust
• NGK LFR7AIX spark plugs gapped at 0.028"
• ID1050x Injectors
• IAG TGV Delete Risers
• IAG or Radium Fuel Rails and Lines
• Cobb Fuel Pressure Sensor or equivalent

Mild Turbo Upgrade Level (18G, or similar ~375whp max)

• ACT HDSS Clutch Kit
• GS TMIC or ETS FMIC

Moderate Turbo Upgrade Level (20G, Dom 1.5 or similar ~425whp max)

• Hybrid SD Kit (AEM 3.5 or Cobb 4 bar MAP Sensor and AEM IAT Post Intercooler)
• GS EWG Uppipe with Tial or Turbosmart EWG

Reasonable but not required upgrades

• Tomei, Cobb or Perrin Turbo Inlet
• HKS or Killer B Equal Length Turbo Manifold
• Killer B Oil Pump Pickup
• GDT Cylinder 4 Coolant Reroute

For power levels in excess of these I recommend direct consultation in order to help you tailor a setup to your needs. Upgrade paths can diverge depending on specific requirements.