I just got my tC, so I haven't added anything yet. But I had a K&N on my Maxima, it didn't seem to do a whole lot, I thought I felt a small power gain, but it could have been a 'placebo effect', who knows.

 

That seems to be what a lot of people are saying. After all, it's probably hard to distinguish between plus or minus 2 hp. The air flow seems to be the slightly more noticable difference according to most ppl with a drop-in. I'll let you all know what I think when mine arrives on the 8th!

 

If u want it for HP u can forget that (it'll barely scratch the surface in terms of performance), now if u simply wanted to replace the air filter (like i did) than go for it (K&N).

 

As a follow up, I installed the K&N, i didn't notice any horsepower improvements. It was a bit of a pain to get it in b/c it is not a good fit. The throttle response is where I noticed a difference, but the little extra amount of airflow coming into the engine is minimal with a drop-in it seems. For real results, such things as removing the catalytic converter (which causes a lot of resistance) would be necessary - which is of course not an option. For horses, go with something else like a CAI. For $38 however, it wasn't a bad investment for throttle response and longevity

 

Thanks to our buddy R2D2, I would like to revise my follow-up. I actually put the filter in reversed such that it was very hard to close the air box. I was afraid to touch it after I closed it because I didn't want to not be able to close it again, but after openning it and turning it around, I was able to close it again all within about 15-20 seconds. So for those of you who are doing the install - just play with it. It is truly a drop-in!

 

PM SmartAss, they got the K&N to me for $36 shipped via FedEx Grnd.