Is there any performance gain or sound difference using a TRD air filter?

 

The performance gain should be similar to a K&N. I don't know about the sound. Mine is waiting at UPS for me to pick it up, so I might have more to tell you tomorrow.

 

I've got a TRD filter in mine since minute 1 of owning a car (it's the same as in corolla/matrix, so i just used my old filter)

I never drove with the paper filter, so can't say if there is a performance difference, but since the filter is so small for a 2.4, plus it's paper, there is a good chance that TRD/K&N will add couple ponies. Soundwise you *might* notice a difference at higher RPMs (4.5K+)

Need to try it with a paper filter when I get home.