While your into the basic's I would advise you to go a little further and do a complete throttle body clean and Idel air control valve clean up as well.
Your plugs are Bosh, made for Volvo, you can get them at Advance Auto, I have been useing the new e3 spark plug for about 6 months now and the car has never been smoother, cost about the same as the Bosh 4 prong plug which I have also tried.
Since the vacuum hose broke off the fuel presure regualtor, you should take that as a hint the other hoses are probally in the same state of decay, you can buy the ends for the hard core vacuum hose that Volvo uses at Advance Auto as well.
Vacuum leaks can creat all sorts of havoc , especially on gas mileage. There is an oring int the vacuum tree that all the vac hose's runn off of. You can remove the part with a 10mm socket and then pull the part out and replace it with a new one, a lot of air can come by this.
When your changing out vacuum hoses it's best to do all at onece, replace one and that will normally cause strees on another till it fails.
Hope that helps
poolman