Plastic vs metal injectors, there are no issues running plastic injectors in general. Just make sure the impedance is correct for your application and oring sizes and height match up exactly with what you currently have.
If buying new plastic 'oem' injectors on ebay they are most likely china fakes, unless it is a ford dealership that sells on ebay. One of our local ford tuners has been having issues with customers bringing in cars with knock-off injectors installed. They looked mostly correct and had part numbers molded in them, but actually side-by-side to an oem it was obvious that they were not real, from the shade of the color to the font of the numbers, but it really showed when dyno tuning with them.
When buying new OEM unless you are getting them from a Ford dealer/distributor you don't know what you are getting. You can pull what you need yourself from junkyards, but to send them out to have them cleaned and tested (if you decide to) will cost almost as much as just buying brand new.
What engine do you have, a 4.0 ohv? And what injectors are you looking to use?
looking for some patrons who have ran these bosch plastic types as to get some performance data ...I know what you mean to ad insult to injury I was having probs after a head job to find it was a bad crank sensor that I purchased for the job (running erratic)...more recently bad relays ...........:/ that's two sets of gaskets on old tommy … if I take out the pill I get some surging im looking at some from hp27fx referred by another member