1989 Honda CRX HF keeps throwing Code 12 and has for the past year, after I replaced my EGR valve and cleaned the port in the intake I still have the code and same symptoms and I am confused as to where to look next. It only happens at certain speeds, I could dive for 30+ min below 35 mph and no code or any symptoms but when going at speeds of 40 mph or more causes it to go off in 20 seconds or less. It shows no symptoms of EGR issues before the code comes up, but after if has a very slight rough idle for no more then a few minutes, then goes back to normal that is the only symptom I have. I have, on a cold start accelerated to 40 mph and no more then 20 seconds later it goes off, I have drove for 20+ min until the engine is at operating temp below 35 mph and no codes but when accelerated to 40 the code goes off as usual. Anyone have any suggestions?