91 blazer TBI rough idle

[Scotts91Blazer]

I recently purchased a 91 full size Blazer 350 TBI, sometimes when I come to a stop it will idle rough and occasionally stall, it also had a slight miss like a bad spark plug wire. I replaced plugs, wires, rotor, and cap... This cleared up the miss on acceleration, but didn't do anything for the rough idle. I would say 85% the truck idles properly So, I went and bought a code scanner and code book for $25, it gave me a map sensor code, as well as an oxygen sensor code (showed a rich condition). Talked to several different auto parts clerks (because they all act like they know what they're talking about, even if they don't have a clue) and they all said replace the map sensor first and see what happens because a bad map sensor will trigger an Oxygen sensor code.
Well, I replaced the map sensor, erased the codes from the ECM, and it still idles rough about 85% of the time, but I no longer get an oxygen sensor code, I just get a map sensor code. I did a little digging and found a notation that the ECM will give you this code if your vehicle idles poorly. So my question is where to look next, I did notice a slight fuel leak when I filled up on Saturday, on top of the tank, either where the fuel filler tube enters the tank, or where all the fuel lines come out of the tank I couldn't tell, but wasn't enough to spill any onto the ground. Doesn't the fuel injection system pressurize the tank, would a slight loss of pressure cause poor idleing? Any other ideas. The reason I'm thinking electronic, such as a sensor etc. is if it starts to idle rough and I turn it off the engine and restart it immediately, it clears up.