Poor starting and rough running

Sounds like a tired engine, have yo done a compression or leak down test?

Might be as simple as bad plugs or a leak in a vacuum line, or maybe an EVAP problem. Get OBD codes read and that might give you some direction. Maybe all you really need is an extensive tune-up.

Things should be tested before you replace them to save a buck . Check for proper fuel pressure some vehicles are particular just having it won't do . Are the injectors gummed up ? Ignition module ?