hi i have an 2001 bug impreza estate non turbo the back box it blowing and needs replaced i would like to replace it with a bit of a sporty back box  but i am confusing myself with bore sizes etc. i would ideally just like a back box that will just fit straight on to the standard exhaust. can anyone help 

I can see why you're getting confused... Scoobyworld have them listed as 2.5" bore (same as turbo models) then ones on ebay are listed as 2.25"...

 

Doing some googling to find out if a turbo model back box would fit... where about in Scotland are you?

scottish borders i have been trying to google it all but i gave my self a sore head  i will crawl under car in daylight with a tape measure see if i can work it out 

If a back box from a turbo model would fit (2.5" bore) then you will have no problems at all, certainly when i looked at pictures they certainly seem to look exactly the same! Just need to confirm bore size

Providing the flanges are the same size to allow for bolts to line up and the gasket can provide a seal, going from 2.25 up to 2.5 should be ok. When I swapped my centre+rear that was 3" going on to a 2.5" downpipe with no issue. It was temporary until I fitted the 3" decat down pipe though.

cobra do a 2.25 one so should just bolt straight on and as i get more pennys to spend i will prob do the whole lot in stages