I installed a cold air intake on my 03 Acura TL base, and now when the engine is idling in park, there is a slight "popping" noise coming from my air filter... Would anyone happen to know why this is happening?

 

What CAI did you install? Please post a pic of your setup.

 

 

I can guarantee that the popping noise you're hearing is coming from the bottom half of that intake moving around and hitting the frame where that thin piece of rubber is. If you can, try removing that bottom portion of the intake and bring the filter into the engine bay and see if that noise goes away. If so then you'll have to probably make a custom bracket near the bottom.