Puffing/leaking No2 injector

[In-transit]

Hi All,
Refitting the inlet manifold after a clean up I noticed, on run up, diesel puffing up from no. 2 injector, slim tip type I believe.
A) Is it a remove and replace or remove and put on new seals?
B) Do I do single injector or all?
C) What is the view on cheap (I think) £34 new ones off eBay?
C) Have been trying to sort out pulling air in fuel probs last couple of weeks, should imagine usual new fuel filter (yes genuine ford) seating probs. The injector puffing couldn't be the source of needing to bleed regularly could it, I thought high pressure side could only blow derv out not suck in air? Advice/new brain welcome.
Many thanks for any advice Arran