348 service.

Just change the fuel filters during the engine out major. You can check to see if they are clogged by removing them and then blowing compressed air in them. If a lot of dirt comes out, then it would be safe to say that they were clogged. The injectors shouldn't be changed unless they fail to work. You can have them checked to see if they are are working properly at a shop that is equipped for testing injectors. If the injectors are clogged the shop should be able to clean them out for you.

 

Your not going to cover the fuel filter service in mileage so its down to time,
change it every two years regardless of how much use its getting its a cheap item and as for the injectors id fill the tank half full and go give it a good run with a bottle of injector cleaner in it,run that fuel out and re fill tank,failing that if you suspect a runing problem and the car dose stand for long periods then the injectors may not be in good health due to fuel standing in them for a long time,give it a run first and see how the car feels before writing off the injectors.

 

How do folks feel about Techroline fuel injector cleaner here? Any reason it should not be used on these cars?