hi guys,

Just a quick update in case someone is looking at this issue in the future. Managed to get it sorted - turned out to be a ground loop. According to the link above, one ground goes to the chassis and the other goes to to ECU ground. I found this link :

DIY Z32 AFM wiring Diagram - Rexnet Subaru Forums

...and according to this, the two grounds are connected inside the AFM and therefore it is creating a ground loop between the 2 grounds. Anyways i just cut the chassis ground and connected both the grounds to the ECU Ground and its now working perfectly.

hope it helps someone

Rich