i dont know what you mean, you dont have a twin turbo you have a single turbo if its a golf gti, at 110000 miles my money is on injectors, there is a few checks you can do yourself to rule a few things out
1. pull oil dipstick when car is running if the car starts running badly your pcv is okay
2. check your dv valve for holes, jack up th car and take wheel off then there is 3 t30 bolts to undo, but use an axel stand for safety,
3. check your cam follower undo the 17mm fuel line nuts after you have released the pressure from the bleed valve, then disconnect regulator switch from the top and undo the 3 t30 bolts for the fuel pump remove and pull follower out with finger and check for wear,
if it was any of the above the car would feel very slow after 3000rpm
if it turns out to be a coil pack or a fuel pressure relief valve or a lpf sensor message me as i have spares of these you can have if needed