Leaking injector
 

So after my flush and switch to Mobil1 Full synthetic oil today, I noticed a puddle of gas in the well of my 4th (I think fourth, closest to distributor) injector. I replaced all the seals (one on each). Started it back up and it still leaked. First suspected a cracked injector, but instead I tried putting on a second seal above the first. Leak fixed. Now it LOOKS like each injector should have 2 at the intake manifold. The first three haven't and aren't leaked and they only have the one seal, the fourth took two. Question is, are they each supposed to have two at the intake (not rail) or just one?

Speaking of the car under my username.