159 Cruiser and
AO Silver Member
Join Date: Jul 2012
Location: United Kingdom
Think around that rpm, there are a lot of changes going on:
Swirl flaps open ( could be sticky flaps)
Turbo kicks in (could be Sticky turbo vanes, dirty MAP, or boost sensor on slam panel, small leak)
EGR shuts (when putting your foot down) (sticky EGR solenoid, or leaking EGR).
Might be worth taking the turbo pipe off the end, and spraying some carb cleaner/ EGR cleaner into the manifold, hopefully clean the swirl flaps an intakes a little bit.
EGR and MAP clean are relatively simple.