legacy1820cc

Hi All

I have a jap import subaru legacy with a normally aspirated 1820cc engine(mpfi 16v single ohc).102000 miles on clock.
My problem is that the car starts and drives fine except it wont idle when cold and nearly always cuts out when coming to a stop.(e.g at junctions etc.)
I have disconnected the MAF plug when it's running and the engine cuts out immediately. I have also attempted to clean the MAF sensor with carb cleaner but no improvement. There are also no ECU codes displayed, (connecting green plugs under dash and then black ones to reset ECU ???)

Is it the MAF sensor or the Idle Control Valve ?? How much to fix ??

By the way the car has a Zavoli sequential LPG system fitted and I have the same problem running on petrol or gas. As the LPG system is an emulator type system with its own ECU, I doubt it is causing trouble. The car saves me too much money to scrap and besides I want to do a million miles in it!

Can anyone please give me some ideas as to what the problem might be??