Toyota Repair: Electrical problem, inner fender, toyota tech

Question
I have a 93 Toyota Pickup 22RE, standard transmission 300401Kms. engine when running good is great,however it will start to miss and kinda run on 2 cylinders the tach also jumps around when it starts to act up. I put Igniter, coil ,cap,rotor,wires and plugs. Worked for about a month,I can't say for sure if it happens when it gets wet, but I think it may have something to do with it. Checked fuel pressure and is good even when acting up.Checked wires from igniter to ecm all good.Took ECM apart no signs of corrosion. I am also a Toyota Tech, but this I can't get a grasp on. Thanks  

Answer
The only thing I can think of right now is that there were some problems in the engine wire harness going to the ECU through the firewall, there were some cases where the soldered splice points in the wire harness developed corrosion and created high resistance causing driveability problems, the splice points are located in the harness where it contacts the inner fender well, when the engine is running normally, try grabbing the harness and move it around to see if the engine starts acting up.
Open the harness and check the solder joints for corrosion if you can't find anything else wrong. Let me know if I can be of more help.