try messing with the carbuetor thingy that regulates the idle just unscrew one bolt alittle and tighten the other or vis versa until it runs smoothly,do this with the engine on of course so you can listen to the sounds and have one person the drivers seat to watch that turbo gauge..and let you know of any sudden changes. Be sure you have a good at least half a tank of gas before you try this, revv the engine from under the hood, and listen for any odd sounds as your comming back down to idle, try it a few times so you get to know what your engine sounds like. dont be afraid to revv it up and make the enigine work its self. how long have you had your car? can you know and or recognize the sounds that come from the engine when theres a proublem? its alot like a baby, you get to know the diffrent "crys" or in your case sounds from the engine.