Idle RPM's 1.9 WB | Forum

My idle RPM's have sat at about 1050 (which I know is above spec) for a long time and I have not touched the timing or idle adjust screw. The idle RPM's for no apparent reason now sit at about 850-900 and the idle control kicks in when they drop below that. Basically, everything is fine and the engine has apparently tuned itself and adjusted its own idle. What happened and should I investigate?