2002 Infiniti Q45 engine light on

One trick that we use to figure this out is first try and listen carefully for a hissing or whistling sound, if nothing comes of that, then, take some brake kleen(thats how its spelled) and gently spray it around all the hoses and intake, if you hear a change in idol, then that is where your leak is. Concentrate mostly around the back side of the engine towards the firewall and the brake booster, you prbably have a partially connected hose thats causing the leak