PD150 feels slow until 3.5k rpm

When I got my PD150 it had just had it's timing belt done and if I'm honest, it's a bit slow... That is until you hit 3.5k then it goes like a bat out of hell!
I have checked for codes but there is nothing...
The turbo was rebuilt recently as the VNT was believed to be dirty.

Car has a straight through exhaust and EGR delete.

Could this be a timing issue?
The car starts first click of the key. All the boost pipes appear to be good. I tried another N18 to no avail...

Any ideas?

Other than the egr delete and free flow exhaust, is the car chipped or have any other mods? try to elaborate alittle more on your car.

Hi, no just the mods stated...

Just wanted a cleaner, smoother engine more than performance.
Car is a 2002 Golf GTi TDI PD150.

Everything else is stock