Hi Paul
Just spotted your post, and appreciate it’s an old one! Did you find someone to do this? I am thinking about doing the same thing on my Forester. I’m also near Wantage and was going to give these guys in Grove a call….
https://akperformance-tuning.co.uk/#about
They seem to suggest they can delete EGR and reprogrammed the ECU……so might be able to sort secondary air……(assuming it’s not the thing!)….
Stephen