02 envoy idle problems

I have an 02 envoy and it ran good until about 8 months ago or so... then the service engine soon light came on.. took it to the dealer and they said it was a cam phaser, they replaced that.. light was still on then it started loping at idle enough to make the headlights dim even took it back and they said it was the software... they updated it.. same thing, took it back they said it was the camshaft position sensor, they replaced it.. same problem.. it idles rough with a lope to it, when you start driving it, it doesn't have a lot of power at all... but seeing as this is my daily driver I can't just park it.. can anyone help me figure this out? the dealership has been no help and has just made it worse...