I have a 2001 Sierra c3,its very similar to the silverada ss with all wheel drive and a 6.0 motor except mine is the lQ4 and not the lQ9.It has a built 408 strocker motor in it with a victor jr. mani and a ls2 90mm throttle body and 75lbs inj..It also has a stage 3 flt trans and a vigi 3000 stall.I had a tuner by me change it to speed density and tune it.but it still didn't work,when i drove it home it was fine but when i drove again it went on again and seems to be turning on more and more,can't go more than 10 min without it turning on.It had a kenne belle on it but took it off to see if that would help fix prob,plus i want to turbo it in future,but still the same outcome.Me and a good friend with more tuning expierance than me hooked up the efilive and it threw the po102 and the po405 while idling,and when i took it for a drive it threw the p1516 code.we did a test and set the p0102 and p0405 to not report and no mil to see if the codes were making the reduce engine come on but it still came on.The base tune it shows right now is from a 5.3,so we even tried a base lQ4 tune and change what it told me to for speed density,and changed the injectors to my old tune that was for the bigger inj.And with that tune it threw p0122,p0405,p0102,and p0443 with the lQ4 tune, and it wouldn't let me give it any throttle,and idled crazy.Thinking about buying a maf and starting over from there.Any help would be gratefully appreciated,havn't got to enjoy the truck for almost a year. thanx RON