Injectors can leak.. I bought a bargain set of injectors for a V8 Caddy on e-Bay for $140, brand new..They indeed cured a nasty random misfire problem and I was elated at my genius. But ever since, that instant start at the turn of the key was gone..I learned to hold the throttle open on a hot start. The bargain injectors were seconds, rejects off the test bench and they all drip a little after engine shut-down..
Sometimes CLEANING formerly sound injectors will cure this. Techron or BG-44 work..