Squeaking/Bubbling Noise When Cold. Goes away in 5 minutes.

What is your question?

In the last year or so, my car makes what I'd call a squeaking/bubbling noise when cold. It's not very loud or anything, but it's noticeable -- even more so when the clutch and/or gas are depressed. This only happens when the car is cold, and the noise goes away in 5 minutes or so -- by the time the engine temperature has stabilized I recently had a 90k service -- all fluids were flushed, a few hoses were replaced -- but the sound still remains (although not quite a strong as before). Any ideas?