I have a Saab 9-5 stationwagon from 2004, with 198000 miles and i have two trouble codes. P1110 and P0134.
I'd start by checking wiring to O2 sensors and boost control valve (and inspect the valve). Age, model and miles aren't in your favor re: money your gonna need to keep it going trouble free. I think that year had poor wiring (cheap insulation that breaks down over time) and if my memory is correct, a systemic issue with all wiring in the car...ie... gonna get worse and involving other systems. Do you see cracked insulation on wires under hood? If so... I stand 100% on above.
My recollection is that Saab got a batch of bad wiring from a supplier in 1985, and that was used in 1985 and early 1986 models. (Ages ago I had a 1985 900 that had the disintegrating wiring problem. It still went nearly 400,000 miles but not without playing a lot of whack-a-mole fixing wiring as the insulation deteriorated.)
GM did a lot of cost-cutting and decontenting when they took over but I haven't heard of the 9-5 having that kind of problem with the wiring, and I've known several people who have them. (I personally have not owned any of the GM-era models.)
For the P1110 code check the vacuum lines, paying particular attention to the turbo bypass valve. The car is 17 years old and is likely to have cracked vacuum hoses.
The P0134 code is related to the O2 sensor. Always be sure to use a genuine Bosch sensor. The Trionic ECU harness has a splice labeled J16 that can cause this problem. According to the Saab WIS (Workshop Information System), this is located about 20mm from the main computer bundle zip tie where it goes into the ECU. (I found this information on a Saab-specific site). Here is a photo of the trouble-prone splice:
There is an online copy of the WIS available which can be very helpful in diagnosing problems:
