hi have a audi a4 b7 2.0 TDI just lately i'm getting loads of black smoke around 1000 to 2000 rpm in any gear with lack of boost then after 2000 it kicks in and everything is ok. in the past the car has had a full remap de catted and EGR removed and had a new turbo last year. car been running great drove to south of france and back 3 times been to spain in it great on long runs. but now this black smoke problem. did diagnostics and was throwing up a fault for wiring harness to the glow plugs so changed harness and glow plugs fault gone. but still lots of black smoke. also changed the maf sensor and had a look at all the pipes going to intercooler. the main pipe at the bottom going to the intercooler has no cracks or anything but looks like it could do with a new o-ring would this be enough to cause the black smoke. i'm running out of ideas and it feels like its getting worse.