You need to be checking all the air intake and breather hoses for possible leaks.Also make sure the throttle housing and butterfly flaps are clean.This is same engine as Golf.

you need carb cleaner. try Toolstation if you have one near you or Halfords otherwise.

Use an old toothbrush and some cloth. spray the cleaner onto these and use to clean the throttle body and butterfly. do not swamp the body with lots of cleaner (on newer cars, manufacturers of throttle bodies WILL NOT warrant bodies if there are any signs that any cleaner has been used on them!!!).

I've found that keeping the throttle body clean helps to keep the engine running smoothly and economically. Especially pick up from low speed.

If you have a turbo, keep the compressor clean periodically too.