171, 174...both banks lean and or rich. truck runs decent, but I cant get the codes to clear. I have replaced the o2 sensors, and when I replaced the sensor after the converter the codes cleared for about a week, then came back on I also get the 1151 code I think it is, and have been told it is a dealer code, whatever that means. I also get the MAF code, but I replaced the MAF and it didnt change the prob, so I installed the old one back on. I have a K&N air filter, and I make sure the MAF sensor is clean from the filter oil(which btw commonly causes MAF codes ) I dont know where to look from here...EGR? oh the fuel filter, pump and regualtor are all new, and I have the correct amount of fuel pressure...36 i think it is, the regualtor is working fine. I cant find any vacuum leaks. I did hollow out my pre converter and converter about 3 years ago, but it ran fine up until about a year ago when i started having the engine code issues....any ideas? I dont want to just throw money at the problem i need educated guesses, and I want to fully go through what I can at home before I even attempt to take it anywhere and have a shop tell me I have a 2200$ problem lol