Obviously not enough installation fluid.
They can be finicky allright but a couple of things... the smaller O ring is the right size, guess it must be as they went into the recepticle ok. If you are using new large rings, they can be a bit big depending on where you got them and prevent the injector going all the way in. The metal plates that keep the injectors in place the right way around? ...flat side to the injector and the ribbed side out for the nut to ride on and push the injector in. If the injector is in properly, the plate is just about flat to the aluminium.
Tip when installing new hose is to think ahead as to the location of the clamp screw/nut so if you have to tighten them you can get at them.
When you think it is all together and running well, let it idle for a bit with dry shop towel under the injectors/hoses. the things might still leak with a bit of time under pressure.
Just a few issues I found when mucking about with my injectors.
Chris
Second try no fuel leak, but still sucking air around 1 and 2 injectors.Pretty pissed by now.One good sign,when you can keep it running and rev the motor it revs freely and quick!!Try the third time,now its sucking air thru #4!!!I can tell where, as while I try to keep it running with one hand,I spray a little brake cleaner with the other.That is it..I had to come in before my temper got the best of me.Am I doing something wrong?Could the new hoses be a bit short?They seem to be all the way in,but they obviously arent.Pretty frustrated at this point.Found myself looking at MG's and Triumphs on Ebay 
