Come to think of it, I think I might have had that sound even before I installed the intake. My mechanic was pretty convinced that it was the Manzo cat-back that was causing the sound. I may see if I can track down another stock suitcase muffler and see if the noise goes away. Although that's easier said than done I'm finding.
I started my car, let it warm up, then I popped the hood and pulled the dipstick, the car immediately sounded like shit till I pushed the dipstick back in. Does this mean that my PCV valve is working?