I have a 2.0 non turbo impreza 2000 model, on my mot my lambda was just bellow limits and i have quite a bit of hesitation when cold and doesn't feel as pokey when warm, would it be safe to say my lambda is on its way out? 

Could be a few thing mate 

 

Oxygen Sensors

 

PCV Valve

 

Coil Pack (non-turbo)

 

Coil Packs (for turboed cars)

 

Spark Plugs

 

Spark Plug Wires 

 

Dirty Injectors 

 

Dirty Throttle Body

 

Dirty Electrical contacts on MAF or MAP sensors (Simply use Electric contact cleaner on the contacts. Do any you can find really,
it's not bad for them.)

 

Dirty or failing MAF or MAP sensors

 

Blocked, Clogged, or 'on its way to failing' Catalytic Converter

 

Coolant temperature sensor