Knock on warm idle ???

Here's my issue:

about a week ago, I noticed a knocking noise coming from driver side of the engine. It only happens when the car is warm (running for more than 10 minutes) and only on idle (engine noise might be drowning out the noise when it's running though). If I take short trips (5-10 minutes), I never hear the noise. My oil levels were a little low (below the minimum mark) but don't think that should have done it. I haven't had time to check the compression. The car runs great. No problems on acceleration and the turbo still runs great. Any ideas???

my friend had the same thing happen to his eclispe, and when he started to drive it it stopped. It is probably your oil level, it takes a little driving to get the oil moving around in the head. It has to coat the valves and springs. You should always keep your oil at level all the time, especially in turbo cars. I also change the thickness of oil to 5w 30 in the summer and 10w 30 in the winter, just a suggestion.

It should be the other way around. Thinner oil in the winter and thicker in warm weather. ;) Maybe that was a typo.

I checked the fluids including the oil. They're are all good. The noise is still there though. It's driving me nuts because it comes and goes but as I said before it shows up after 10 minutes or so of driving the car. From then on, it's kind of random but it does increase with acceleration for a couple of seconds only to disappear. I was doing some research over the net and I read something about piston slap where the piston for some reason starts to move horizontally more instead of its characteristic vertical motion. Could this be the problem?