Aha, Mr Burns.. I used the injector service you recommended (InjectorRX in Houston, TX - a very good service BTW)
Yes, I lubed the "o-rings". The difference between the Dorman injector cavities and the stock injector cavities is vast.I wonder how the injectors can possibly seal. It also makes me wonder what other shortcuts were taken by Dorman (they didn't machine and provide inserts for the COP hold down screws, for instance).
Perhaps I should have paid the hundreds of dollars difference for a Ford part ? That is why I asked this question. And thanks for the responses.
I also have a '98 with NPI heads and installed the PI intake on it about 5 years ago now. You don't need adapters, only a dab of RTV in the coolant ports along with PI gaskets, and the PI heater tube. Gained 10-15 RWHP with the swap.
I would not take a hammer to the injectors; that is just asking for trouble. Have you tried tightening down the fuel rails some to make sure the injectors are all seated properly? I can't remember if my Dorman Intake had coned shaped interfaces or not, but I'm sure they did. I'm sure someone else more experienced than me will chime in, but it seems like if you had an issue at the injectors not seating properly, then you would have a fuel leak there. If you don't have any fuel exiting out near this area, then I would say you don't have a problem there (other than maybe a bad injector).
How many miles are on the car? Have you changed the PCV valve? If not, I think this can cause idle problems as well. If you have a friend with a 'Stang, see if you can borrow someone's IAC Valve to see if that is the problem.