idle dropping at start.

Okay so my car was fine when I first got it. About a month later it started to have this problem where when started the RPM's would drop to 300-400rpm for a few second then go back up and all was well..

About 2 weeks ago it started to actually stall when it did that. So I went and i replaced the air filter, and fuel filter (this was crap, black gas poured out).. So I went and ran the tank through filled up and I'm back to the low idel when starting the car again.. At least it doesn't stall but what should I try next to fix this?

Injectors? New plugs?

i would also like to know what you can do to fix this because my 94 eclipse is having very similar problems.