i saw the topic on the oils and wondered if i was using the right oil. i have been told to use a part synthetic 10/40 in my import wrx is this true ? can someone shed some light on this for me.

So long as 10w/40, you can use either semi or fully synthetic oil.
It is only suggested that you do NOT fill with 0w/40 oils as too thin for the turbo bearings in this climate.

Depends what 10w/40 grade part synthetic you are using. Your engine will be better protected with a fully synthetic oil of the correct viscosity. Either Mobil 1 Motorsport 15w/50, Motul 300V 15w/50 or Castrol RS 10w/60 will do the job as well as it can be done.

ive just put in 5v50 is this wise?

Thinner than ideal, but it should be okay as long as it's a well-known brand and not "Gold Nuts Value Synthetic" (I kid you not this oil does exist!). What brand is it?