For experts only: Problems 2.3E (NG)

Hi to everyone! I want to briefly explain my suffering story: I drive a 2.3E NG 5cylinder bj 94. The box runs very badly, starts smoothly, but runs very thin and has no performance at all. I changed the spark plugs, the old ones were cabbage black=>too fat… Nix changed…now the new total white=>too lean. Lambda probe I controlled, this works. If I plug them off, it runs the same way. The voltage value is 0.5v un idle. d is changing when gas is given. However, the control unit cannot be read out? I was at several workshops, they told me that the control unit is not diagnostic. You can only read out by means of a flash code. Unfortunately, this was only possible up to bj 90. I have neither the control lamp nor the fuse in the power-off pump relay?? Another thing about the rest of the machine: underpressure is tight, pump works, ignition distributor is renewed, fuel pump seems to be also in order, Ignition is set