[pingpong]

I just installed the system as well, as the sound is amazing.

Unfortunately, it looks like I've gotten a drop in MPG (I've had this system installed for about 300 miles now). On the freeway, I'm still getting around 28MPG, which is what I used to get. In the city, though, I'm getting significantly less than before, with the same driving style. During cold idle when I let the car sit for about 30 seconds, with the MPG counter having gone through half a tank of gas, I'm seeing the computer say my MPGs are dropping from 27.3 to 26.4. That's almost 1/4 a gallon just for sitting there for 30 seconds. If I'm getting 30MPG on the freeway cruising at 60MPH, I could have driven for for about 7 miles (7 minutes) using that 1/4 gallon of gas. The car also smells like it's running incredibly rich when cold. Very disconcerting stuff.

I don't think the intake alone could account for this. Any other possible causes? Leaks, malfunctioning MAF or O2 sensors, etc?