I have a 2002 Focus SVT that I picked up from the first owner, which was thrown all around. I have noticed that the idle has gotten worse since I've had it. The idle sits still but dips down about 200 rpm then returns. The idle is really unreliable at all times, especially when the engine is warm. Additionally, there is a subwoofer type noise that happens slightly in the rear right of the car. Sometimes it sounds like slurping and other times it's like a subtle one-second bass. When driving, and cold, the rpm drops really fast when changing gears. When coming to a stop, cold or warm, the idle is iffy. It will either sit way above at 1200 rpm the slowly drop when I am fully stopped or wave around trying to stall. Every now and then it will stall when coming to a stop. Lights also hazy in the LCD screen and speedo lights just slightly, more of a shimmering dimming. I changed the MAF, IAC Valve, Ignition Coil, Spark Plugs, Spark Plug Wires, Cleaned the Throttle Body, and more. The Idle speed is about 850, though moves around too much to know fully. It has a short ram intake currently by AEM. Any ideas of what to do to fix it???