Lot 3068: 2004 Subaru Impreza WRX STi

Based on my research, here are the best engine modifications for your 2004 Subaru Impreza WRX STi with the EJ257 engine:

Stage 1 (300-320 WHP) - Reliability & Daily Driving

Since your car already has a COBB intake, you’re essentially at Stage 1+. The key mods are:

• ECU Tune (COBB AccessPort) - Already beneficial with your intake
• Upgraded intake - ✓ Already installed (COBB SFI)
• Cat-back exhaust - ✓ Already have TOMEI titanium

Stage 2 (320-350 WHP) - Best Bang for Buck

• Downpipe/J-pipe - This is your next logical step since you have the cat-back
• 3-port Electronic Boost Control Solenoid (EBCS)
• Professional tune - Critical for reliability

Stage 3 (350-400+ WHP) - Serious Power

• Turbo upgrade (since yours is still stock)
• Fuel system upgrades (pump, injectors)
• Front-mount intercooler
• Upgraded clutch

Critical Reliability Mods (Do These First!)

The EJ257 is notorious for ringland failure. Before chasing power:

1. Air/Oil Separator (AOS) - Prevents oil ingestion
2. Upgraded oil pickup tube - Prevents starvation
3. Oil pan baffle - Maintains oil pressure
4. Proper tune - Rich AFR and conservative timing prevent detonation

My Recommendation

Given your low mileage (15k) and existing mods, I’d suggest:

1. Add a downpipe and EBCS for Stage 2 (safest power jump)
2. Install AOS and oil pickup for reliability
3. Get a conservative pro tune

This should net you 330-340 WHP while maintaining reliability for daily use. The Stage 2 setup is widely considered the sweet spot for EJ257 reliability vs. performance.

Want me to help you find similar modified STis for comparison, or do you have questions about any specific modifications?