There are two main drawbacks I can immediately think of:
1) The extra torque may affect the clutch. Now, this is not a direct effect as the clutch itself will no doubt be rated miles beyond the existing engine output. The problem is that drivers tend to 'ride the torque' on remapped oil-burners i.e. get lazy about changing down. That is the real cause of early clutch failures (IMO).
2) Upping the boost pressure, BHP and torque will find all the weak points in your car. Although it may be entirely reliable now, at 168k the joints, hoses, bushes and mounts will be well on their way. Putting extra strain through these components may tip them over the edge.
I remapped a 10yo Audi A3 1.8T (petrol). The main failure directly caused by this was a burst turbo hose as the turbo was running hotter and at higher pressure. It was an easy fix with a replacement high-temp silicone one, but I shit myself when it went as I was doing 70mph and it went pop!
If you have anything like a dual-mass fly wheel it may help that to expire.
Another big complaint is diesels becoming v. smokey after a remap. This is unburnt diesel and is caused by the settings of the remap itself, a diesel should be able to be tuned without this happening.
I don't really know anything about SAAB as I was in to tuning VAG engines, but the principles are all the same. I'd get on an owners forum and look for a recomended tuner and talk to them.
