Hello there, do I recognise your name from the volvo 480 club europe forum (now sadly departed)? I had a 480 turbo prior to my C VR6. I've actually had 2 turbos(with bleed valves around 0.9 bar boost IIRC, but std ECU) and 1 ES in my time.
Dunno about autoboxes however but manual version of 480 turbo is no match for VR6 'rado, at least in the state of tune mine was in. Get VR over 4000rpm and it takes off like a scalded cat!
Get one, you know it makes sense!!