The item shown is actually the idle speed actuator, on a phase 1 GTV the ECU is a fairly large metal box found in the passenger footwell with a PCB inside.
They do vibrate when energised though, nothing to worry about if your idle is constant, when they fail the idle will hunt and the engine may stall as the revs drop when stopping at junctions etc.
The cause of many an idling problem as they can get bunged up with oil deposits from the breather system, sometimes cured by cleaning the innards out with some sort of solvent.
IIRC they are quite pricey from Alfa, and sometimes needed if cleaning fails.
Sprint - 33 - Sprint - 33 - 155 - GTV - GTV - 156 - GT ...gone German for now though.
Last edited by Alfa Seltzer; 24-07-11 at 23:37.