2008 Sierra 4.8L, 4L80E, longtube, CAI, 229/235 | .610?/.610? | LSA111+2 cam. I have a tuner who has done several cars/ trucks and they went really smooth and dialed in perfectly. This truck has been a nightmare from the day I received it. FPCM dead, purchase another, license and dead after working for a couple of starts. pump is wired through relay, bypass regulator set to 58psi (rail shows 58ish). Segment swapped for 4L80 which is working good, but the tuner has said for the last week that there is a vacuum leak, possible pushrod length issue. I hosed the intake with brake clean around the ports, hoses, sensors, pulled intake to check gasket mating (new ac delco gaskets), disconnected all the vacuum lines and capped them. Pulled valve covers and checked lifter preload (between .068"-.072" I believe), all to have same results 76-80ish KPA at idle. I hate wasting his time with issues not tune related and I'm lost with this. I'm attaching the log file which I minimally understand but see the map kpa where he says, what I need help with is possible ways to narrow down possible causes. At this point I'm open to any suggestions, I sprayed 5 cans of brake clean today alone and don't see any changes. All cylinders show temp readings from 280+ to 300 and go higher if it runs longer. Aside from setting it on fire I have no idea what to look for.
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