Do you mean the 'Idling speed potentiometer'? It looks like a small black plastic cylindrical shaped part, clipped to the right side of the engine bay, with two wires coming out from the bottom to the engine?
If this is the part you mean, I think you can still order a new one from a Renault dealer. Expensive though for such a small part. The wire broke on mine and I was quoted £102! I managed to solder the wires back on instead.
The part number (D501 Z7U engine type) is: 77 00 722 068 (Take a look at:
http://www.jordan-alpine.de/FrStandard. ... g_v6gt.htm)
I found though, that my car still ran fine without it even connected! It just meant I wouldn't have been able to adjust the idling speed and I had an electrical warning light and service light constantly illuminated on the dashboard.