(T) Dodgy Idle and stalling

Another new prob (i really am hating fiats now).
When the cars warm (done it twice now when cold too) in traffic, go to put it back into gear, put some rev's on and it just dies, if i jump on the throttle to the floor it keeps going, but if you are just gently moving around in traffic it keeps stalling (which doesn't look good).
Any reason why this could be happening??
Garage told me to disconnect the batt for a few hours to kill ecu, did that and after wards it still did it.

Beside the basics i'd start looking at the throttle body potentiometer.

My wifes '98 Sporting had a kinda similar problem. At certain loads, the engine would "miss" and chug a bit. If you dipped eh clutch and gave it a bit of a rev, that helped a bit. Not ideal though. At the weekend I cleaned the throttle butterfly, checked the plugs, leads and coils, disconnected the battery for a while and unplugged all the engine bay wiring loom connectors. I plugged and unplugged the connectors a few times to see if there was any dirt or corrosion on the pins. I noticed a bit of corrosion on the lambda sensor plug which could confuse the ECU. I took it a run in town the next day and it still chugged a bit.
My wife only really uses it for wee runs into town etc, it never gets a good kicking if she's driving it. I took it out the bypass to work on Monday and all was well. It may just need a good thrashing now and again to clean it out.