Flaps? What flaps?
AO Silver Member
Join Date: Oct 2014
Location: United Kingdom
Usually down to a vac leak on the VNT system.
Have a look in the fron tof the engine bay at the small vac lines that go to the actuator on the turbo - a split/crack in one of these will cause the turbo to get stuck in low-boost bost, so the car will feel very lackluster until 2500-3000 rpm... I had it myself when I broke the connectors to the VNT solenoid valve (careful! it's quite fragile!)
Pretty common fault, as the original hoses will get brittle over time. Replace them with some 3mm silicone vac hose, and you're all good.