yukon_denali_05

I would say just go first with the 2 upstream the cats. If they've never been changed then I would change them. Make sure you get OEM O2 sensors and no aftermarket crap

That sounds normal to me. Looks like fuel pressure appears to be good. I think you are on the right track with next guess being O2 sensors. How many miles on the truck and do you know if 02 sensors have been changed yet?

I had the same issue. I thought it was the fuel pump but before changing the fuel pump I checked fuel pressure. I changed the fuel pressure regulator and it did the trick

I've been a member here for a few years and active on and off... But I've been on more often the last few weeks and I have to say that there are ALOT of nice rides here... I thought I would share mine as well. 2005 Silver Birch Metallic Yukon Denali XL - Custom Wester's Tune - Corsa Touring Exhaust - Eibach front and rear stabilizer bars - Volant CAI - MSD Super Conductor Ignition Wires with AC Delco Iridium plugs... - AMSOIL blood line with Royal Purple engine oil - Escalade third brake light - Escalade vent caps - Cooper ZEON LTZ rubbers - LED tail lights - ALL HIDs 5k Soon to come... Ceramic coated LT headers...

I drive my truck very little. About 20 miles a week on avg and maybe do a 300-400 mile road trip once every 6 was. I have 6.0 and very solid engine. I typically change my oil every 5k miles or 6 mths. I use 5 qts of royal purple 5w-30 and 1 qt of Lucas synthetic engine oil stabilizer. Truck maybe burns less than half a qt. Shes got 70k miles on her now.