Q: running even leaner on 2002 Chevrolet Camaro

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It's been a couple months since my last post here, but the same old problem presist. My long trim fuel trims are a positive 16-20 crusing. They used to read negative with no changes to the tune or mods. I have tried another mass air sensor, tps sensor, tested fuel pressure idle and cruise good at 60 psi, my 02's are good and switching fast, tried fuel injector cleaner and a seafoam intake cleaning. None have worked. Of anything the car is running leaner now than it did since my last post here. I have though vacuum leaks and sprayed intake cleaner around the intake gasket area's and all the pcv hoses have been replaced. Also replaced fuel filter.I doubt it's a vacuum since my short trims aren't high at idle and then drop with throttle. Read about that online. Map sensor maybe. I just had the driveside cat replaced last week under a extended gm warranty and am affraid of it doing bad again.
(1) Answer
Vacuum leaks are by far the most common cause of high fuel trim numbers, your 2002 Chevrolet Camaro included. The best way to check for vacuum leaks is with a "smoke" machine. These machines were developed to test the EVAP systems on our newer vehicles but are also very effective in locating vacuum leaks. The machine will fill the intake system with smoke under low pressure. Areas where smoke is coming out are potential vacuum leaks (slight seepage of smoke around the throttle valve would be normal).