Are there any warning lights come up when this fault occurs at any point?
Any unusual noises from the engine or any problems regarding the gearbox at anytime?
What things have been checked or replaced so far upto this point
Ok...Well the engine management is likely something that needs to be interogated at least to see what fault codes either history or pending or current is stored so that would be one thing to address first..i note you mention the turbo waste gate being cleaned..i cant see how they could do that as the turbo on these engines which is pretty tight to get to added to that the waste gate on the turbo is vaccum controlled..so if the waste gate on that is sticking then its likely the VNT mechanisim stuck with carbon inside the turbo exhaust housing.....One of things thats quite common on these is the inlet swirl flaps and the egr passages/thottle body falp becoming blocked or stuck with carbon build up..and this can cause a power issue aswell as set various EGR /Flow fault codes...This is all on the understanding that the DPF diesel particulate filter on the exhaust is not partially blocked..they can check the saturation percentage levels on diagnostics and force regen if required..but as above id maybe be lookcing at the swirl flaps especially so the rod that actuates the flaps isnt broken and moves..aswell as ensure the egr valve is clean and the passages within the inlet manifold are clear..they may have to remove it to do all those checks..I do hope this helps
Yes they are basically a Vauxhall Vectra C base these saabs and use the same diesel engines..and they too can often produce the same syptoms..and normally 9 times out of 10..its usually one of those components or areas above..on the diesel 16v 150 engine..the swirl flaps are a very common problem they need to be freed up or jammed in the open position without any problems to the engine.done it many times on both saab and vauxhalls..the 120 8v is the better engine with really only the egr giving trouble...But yep have them check out all the above and see if solves you issue...But before you log out please dont forget to rate my answer..much appreciated