The saab diesel engine is the same fitted to the vauxhall vectra etc etc (same car basically), which were developed by Fiat, so in actual fact the saab,vauxhall plant is a Fiat ....anyways.....I have just had my missis's Signum 150 in absolute bits due to the same poor running your brother had and I am 100% that egr cleaner as added to the fuel would absolutely not shift the amount of soot in an egr that causes problems all through the immediate induction system, the egr cleaner probably freed off the turbo and unblocked the egr pipe where it terminates at the turbo, they tend to block at the junction with the turbo in the first inch of pipe, once this is cleared the car usually runs ok again, the egr/dpf/injector/induction cleaner (basically the same stuff) is very good at shifting carbon where it burns hot,i.e.combustion chamber,turbo,catalytic convertor etc but when the gasses cool down as they reach parts such as the egr there is negligible effect and the only way of really removing soot and carbon from the egr,inlet manifold etc is to get yer fingers mucky......lol....trust me I am an expert on cdti carbon encrusted engines, I spent 3 weeks removing the said carbon/soot and after removing it all and power not being back to 100% I added a wynn's dpf treatment to over half the tank of diesel (lol I removed the DPF 15000 miles ago!!) and low and behold all was back to good in 30 miles.......I guess the kerosene additive freed the turbo and the egr pipe.
Got to remember most of all these threads are down to the EGR valves not necessarily giving up the ghost all in one go but they slowly over time block everything else up until they themselves stop working in the process, so when the egr is blocked and no longer working then simply cleaning the egr will only extinguish the dashboard light and stop the fault codes, after cleaning the egr then you need to clean the throttle body and then the inlet manifold (thats fun!), I think it is called, "cause and effect"!
When all is cleaned then put some cleaner fluid thru the tank to get where you couldnt with the varying size toothbrushes etc.
Lol...dont yer just love diesels!