94 2500hd 454 Erratic Running

[Dal2HS]

First a list of things replaced... Knock sensor, plugs, ignition module, temp sensor. The truck was starting perfectly until I installed the new ignition module. It would run fine until warm...then would start to struggle and run really rich. It would do that for a while then start running great. When it runs badly, the gauges tend to pulse and it bucks like an angry bronco. My mechanic friend suggested a new ECU as it's constantly throwing the code 43 even with a new knock sensor and because of the erratic running. Of COURSE it's the one that's not stocked at the local auto parts store so I had to order it.

Any suggestions on what else it could be? I did a seafoam treatment. I thought about the fuel pump but that wouldn't trigger the running rich code from the O2 sensor. Also, after I replaced the temp sensor it triggered a code 15. I'm getting a new plug for it tomorrow. I SURE appreciate any suggestions as I would really like to get this beast on the road.