You should try intake cleaner. It atomizes better than WD-40 and won't leave a mess all over what you sprayed. Just be careful not to get any on the hot turbo. (Well, you should get WD-40 on it either for that matter).I am having the same problem. I checked all the hoses for rot but did not see any problems. I do however hear a hiss on the passenger side at the firewall. I am thinking that it is a leaking intake manifold gasket. I tried spraying some W-D 40 to note a change but I don't think I hit the leak. I have a feeling it is underneath.