Originally Posted by fearnight

The general consensus with the 2UR-GSE intake is to keep the stock airbox and use a drop-in air filter. Frequently, the aFe dry filter and Tom's Racing filter are recommended.

When I had my IS-F, I purchased both of these air filters. I didn't feel any difference between them and the stock air filter. I almost felt a slight loss in power, but I didn't have any data to it back up. I swapped back to the stock air filter and was happy.

I now have a GS-F and using OBD Fusion to gather some actual data. I recently changed the stock air filter (<500 miles ago), so figured this was a good time to test it against the drop-in filters I have. Both my aFe dry and Tom's Racing filters have less than 250 miles each on them.

Intake Mods:

• RR Racing carbon heat shield
• HPS silicone intake tube (post-MAF so shouldn’t affect the readings)

Test Conditions for all filters:

• Hood open
• Inside garage with door opened to the rear (no fans or outside airflow to the intake)
• Coolant and oil temps at full operating temp
• “Normal” drive mode selected

OBD Fusion:

• Comparing the Mass Air Flow Rate (lb/min) at various RPM's
• Idle reading, holding RPMs at 2,000, then 3,000
• Using OBD Fusion "log" graph feature to measure readings

Results:
All MAF rates below are measured in lb/min

Stock air filter
Idle: 0.690
2,000 RPM: 1.500
3,000 RPM: 2.660

aFe dry filter
Idle: 0.695
2,000 RPM: 1.580
3,000 RPM: 2.700

Tom's Racing filter
Idle: 0.650
2,000 RPM: 1.500
3,000 RPM: 2.580

Since the Tom's Racing filter seems to be the forum favorite, I ran the exact test 3 times in a row with the same results.

Conclusion:
The aFe dry filter does seem to show a slight improvement in airflow compared to the stock paper filter. This makes sense due to the larger pleats.

Unfortunately, it appears the foam design of the Tom's filter has a slight airflow disadvantage compared to the pleated stock and aFe filters.

I've decided to stick with the stock air filter. To me, it's easier to just drop in a brand new filter than continually clean the aFe dry.

These results should apply to all 2UR-GSE vehicles, including the IS-F and RC-F. Hopefully this data is helpful to you as it was to me in my air filter decision.