Ok here goes,

I am helping a mate with his VY Calais sedan. The car has been converted to manual previously from auto. Car has a 228/228 114lsa .590 lift Comp Cam. Car was previously tuned we believe as a auto with the cam and then converted to manual. The car was hunting around 1400rpm and 1800rpm light throttle and when at idle the revs would jump up to 1500rpm for no reason. We replaced the PCM due to the existing tune being locked. When idling for more than 5 min it would throw a P0121 code

The car was retuned and was good for a day or two.

Now the car is hunting bad again and mil p0121 is appearing again. I don't have a tune here to load yet, will do that tonight along with a log.

The main issue is the hunting. I have flattened the timing in all spark tables to 24 degrees from 1000rpm to 3000rpm and to .36 odd g/s however I am still getting hunting, the spark in the logs does not change, map does not change and fueling is ok.

Does anyone have any ideas at all as to what might be causing these issues, it is doing our heads in.

Thanks Nigel