Running Rough / Missing on a Cylinder 98 sohc

[backroads]

So after replacing the upper and lower intake gaskets, checking the plugs, replacing the plug wires, it still was doing the same thing.Took it to a local garage ,and they told me that injector 4 was dead, replaced it and no change. Still missing. Maybe they told me the wrong injector to replace.I'm thinking they should rediagnose.
How do you check for a bad injector?There's no cel.

 

[jahzwolf]

swap them and see if the problem moves ..

 

[backroads]

So it's in the shop again for further diagnosis,supposed to be done today by lunch time.If they can't fix it again for another $90.00 I'm probably just start swapping out sensors,etc.One thing that comes to mind is a dirty MAF, it's never been cleaned, but could that cause my problems? And what things should I start replacing first?How bad would it run if a cam chain jumped a tooth?

Thanks for any input.
Backroads

 

[backroads]

Ok fixed it. It was a combination of a bad injector, dirty MAF, and mainly, the Bosch Platinum plugs!! The guy at the shop said they see many problems with those, 2 of them were misfiring, one was dead. I checked them and they looked good but they weren't.
They said that they always use factory origional plugs bought from the dealer, costs more but worth it. Using Motorcraft plugs now.Yes I installed them myself, which saved me $200.00 on labor.
Next up is the vibration from the drivetrain somewhere.