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Modifying exhaust system on BMW E46 325i (M54B25) - effects and costs

Exhaust modification options:

• Catback exhaust system
• Headers
• High-flow catalytic converters

Potential gains:

• Power increase: 5-15 HP
• Improved exhaust note
• Slight weight reduction

Popular options and estimated costs:

• Magnaflow catback system: £500-£700
• Supersprint headers: £600-£800
• Eisenmann race exhaust: £1000-£1200

Installation considerations:

• Professional installation recommended (£150-£250)
• May require ECU remapping for optimal performance
• Ensure compliance with local noise and emissions regulations

Note: Combine exhaust modifications with intake and software upgrades for best results.