NAY TURBO 99

hi everyone right my mate has just brought a 95 wrx import he has had it about a week and decided to get it belled up he has had an rac trackstar tracker and a clifford concept 650 alarm and imobiliser with remote start
and since it has been fitted every time he slows down or presses the clutch in to change down a gear it cuts out but does not cut out if you change up the box the guy who fitted it has had it apart twice and cant find any probs he has changed the maf just in case but to no avail any one else had any probs like this or got any ideas what it could be cheers