98 s70 non-turbo 120k. It was throwing cylinder misfire codes too but I gapped my plugs and they haven't come back after 30 miles of driving, fingers crossed. Did front o2 sensor, MAF, and p0172 is till there. Vacuum diagram confuses the hell out of me but what i think are the vacuum lines look OK. 2 questions but any input welcome:
1) since I can't find a vac leak but am not confident in my ability to find one- is my money better spent replacing all vac lines or paying for a smoke test (I don't know how much $ they cost)
2) Is there any regularity in the vac lines (marking, texture, etc. ...) that would help me find them all.

 

Hey, I am having similar issues and my shop only charged me 25.00 to smoke test it and show me where the leak was coming from. Unfortunately for me I fixed the leak had it re-smoked and still have an issue.

Good luck.