2007 Silverado 5.3 idle and AFM issues

I received an SOS call from a guy with the following issue:


07 Silverado 5.3 gas souped up/cammed and custom tuned by unknown with unknown equipment by previous owner

Motor blew

09 5.3 stock installed with the same tuning

Purchased by current owner:

Ran good but idled excessively high and “took off” to approx. 1500rpm once you started to roll out.

Had dealer flash to stock file thinking it would correct it. Now he says it starts but is in “4 cylinder mode”. Not sure if his assessment is correct, or just a limp mode of sorts.

Truck is an hour away so I'll be laptop only. Speculation is that maybe the previous owner dismantled some of the AFM components and as a result may be in a limp mode?

Finally getting somewhere. DTCs: P3401 p3425 p3441 p3449

Initial suggestion made to him to locate the likely unplugged connector and plug it in. Probably will run just fine unless parts were removed.

If someone happens to have a stock base file for 3GCEK13M97G513628 I would appreciate it.