Rather surprised that the diagnostic has not shown up any fault code. There are quite a few things that could cause idling problems hence the diagnostic would help considerably.

Things to check would be:

1. All air /vacuum pipes connections.

2. IAC ( idle air control valve)

3.Throttle valve sticking/linkage.

4. TP ( throttle position sensor)

5.ECT ( engine coolant temp sensor)

6.IAT ( intake air temp sensor)

7.MAF ( mass air flow sensor)

8. MAP ( manifold absolute pressure sensor)

Rather a long list so you may need the help of a "good garage" to inspect and check the above .