Boyzy

Morning lads and lasses. I bought my Astra twintop 1.9cdti nearly two years ago, I had problems with smoke and power so had the dpf welded up and remapped. Smoke persisted so garage told me I needed a new injector which cost an arm and a leg. Three new injectors later and still the same. I've cleaned my egr valve and my boost sensor yesterday guess what... still smokes terrible and no power below 2000rpm. No engine management light is showing either. If anybody could help I'd really appreciate it. Boyzy