Currently checking for boot leaks on the Colt and have them all sorted but one, and it's a pretty significant leak around the #4 injector where it seats into the head. I switched lower seals with another injector that wasn't leaking and the leak is still there at #4.

I can assume that the seals are good since the other injector didn't leak when I swapped seals, so I'm kind of stumped. I see no visual cracks around the injector or head.

The car has FIC 650cc Low impedance injectors, could it be the cushions are the stock ones and not big enough to put enough downward force to seat the injector? That's assuming FIC uses different seals/cushions. None of the other injectors leak though... I bought the car with these injectors and a whole lot of boost leaks.

What happens if you swap the injector not just the seal?

Good call,I just got in and removed all injectors, cleaned, greased and refitted them.

Different injector now has a very small leak, but much better.

Are the top cushions supposed to be a touch loose or are they supposed to be snug? I think I may need specific ones for the FIC's. I had to play around with them a little to stay on properly with the injectors on the rail.