i have a 2002 saab 93 dti 2.2 i've recently had some black smoke when i pull away around when the turbo kicks in, also sometimes i get a bit of stuttering/missing effect. all filters have been changed and i put some injector cleaner through it. today i cleaned the egr valve and there was a lot of black deposit on it which i cleaned with carb cleaner. i was told this could be a clogged lambda sensor. is this right and where on the engine is it. thanks in advance