You only hear it at low speeds due to the fact at higher speeds other noises masks it. Engine rpm doesn't affect it. As far as left or right its haven't tried that yet.
I am, although it does have a curved crack near the bottom of the passenger side where the temp registration goes. I keep the temp registration on so it hides it. I won't replace it though until after a trip I have coming up this summer.
CARB isn't going anywhere. The Federal Govt. can cut the funding to it but that may actually hurt us as parts in the pipeline waiting for CARB approval would probably be indefinitely delayed.
To be honest if its quite hidden, which they usually are, I don't think you would have any issues with an intercooler. I live in Cali myself. Just get one in black and it pretty much fits in the OEM location. There are quite a few more options than just those. I believe Mishimoto makes one...