Lots of possibilities here and as said without reading the codes it will be a stab in the dark.
Common causes:
- Misfires (Bad spark plug, ignition coil, fuel injector. Bad DME software - I think progman versions v32-v34 had some bad adaptations that would cause misfires on Bank 1 (cyl 1-3) on longer journeys. Updating the software is the only way to fix these. )
- Boost leak (Substantial leak, e.g. FMIC pipe popped off. Would trigger on WOT)
- VANOS (Vanos solenoids may need replacing)
Get the codes read and let us know.
Does it disappear if your stop/start the engine, or leave it for an hour or two? Does the engine feel lumpy or doesn't run as smooth as normal? Most of the above issues are fairly easy to fix and not too expensive, but it depends on if you know a good indy and if you have a bit of patience. Dealers sometimes take the big hammer approach to this and replace a lot which is fine when you have warranty. Out of warranty, paying ~ £2K for 6 new injectors is no fun and everything else should really be tried before spending this kind of money.