Injector seals

I,ve managed to remove /replace  3 of my injector seals but I'm having difficulty removing no3 inj.seal (second from left ). I made a little tool to remove them which worked ok for three of them but this injector will not budge, yes,I have soaked them in Plus Gas. Does anybody out there have a different more successful way of removing these.

Removed mine just yesterday, again 3 of them were no problem one was tight as b_ggery, soaked for a while and just get tugging, levering eventually came out with a little levering behind the fuel line nut  

I had the b@@@@r .Ditched the tool I made, although it was successful for removing three of them, went back to the good old open ended spanner technique used it to lever up against the injector and out it popped.
Checked the timing, adjusted the idle speed and leak checked, all ok. Took it for a run, seems to be running smoother, but, it could be my imagination.