I changed the oil in my 99RA a few weeks ago and this weekend I noticed it's not boosting as quick as normal, and there is oil coming out of my bov on my fmic pipe, checked the oil and it seems to above the high notch? Could this be the cause?

Cheers

 

It could be, too much oil in an impreza is as bad as too little.

 

If the oil is above the turbo oil return pipe in the sump believe it or not the oil will not go down the pipe and it appears like your turbo has blown.

 

+1 had this happen to me