04-07 STi Modification Minimum Recommendations
Common issues to look out for before modification
- Low Compression or Bad Leakdown
- Incorrectly gapped, old, or completely wrong spark plugs.
- Failing fuel pump and fuel pressure regulator
- Boost leaks and vacuum leaks from brittle lines, torn inlets, failing couplers
- Worn factory boost solenoid
- Faulty or poorly performing sensors (MAF, 02)
- Faulty or failing ignition coil packs
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 (VF ~300whp max)
- AEM Fuel Pump
- COBB EBCS
- Quality Catted Turboback Exhaust
- IAG AOS
- Cobb Accessport
Mild Turbo Upgrade Level (18G or similar ~350whp max)
- ACT HDSS Clutch Kit
- IAG or Radium Fuel Rails and Lines (Including Topfeed Conversion exc 07 STi)
- IAG TGV Delete Risers
- ID1050x Injectors
- NGK LFR7AIX spark plugs gapped at 0.028"
- Cobb SF or Grimmspeed Intake if TMIC, ETS Intake if FMIC
- ETS/GS TMIC or ETS FMIC
Moderate Turbo Upgrade Level (20G, Dom 1.5 or similar ~400whp max)
- Cobb Fuel Pressure Sensor or equivalent
- 73mm intake and/or 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
