Irregular Rough Running

Check first that it may be a grounding problem. Make sure your engine is grounded to the body really well, (Firewall, frame rail etc.) & make sure the I.C.U. box is grounded well too. (Run a separate ground wire for that, it's a good Idea anyway) Car may lose ground when it's warmed up, slight expansion of the metal, paint, a bit of rust, could cause the problem. Just my 2 cents.