Hello, I have a 2003 GMC Envoy with the 4.2l I6, and I'm experiencing a strange stumble at idle. Whenever the engine is warm and idles at 600rpm, if I go to turn the wheel and accelerate, the engine stumbles and acts like it wants to stall, then picks right up. It also happens when shifting from revere to drive, and trying to accelerate and turn the wheel. It has done this for along time, over a year, but it never stalled until one day a couple weeks ago; I had just shifted from reverse to drive. I replaced the vacuum line from my FPR to resonator because it had cracks but that didn't seem to solve my issue. Anybody out there had this and know a fix? I've replaced the upstream O2 sensor, cleaned throttle body, replaced VVT solenoid, cleaned map sensor, and changed the spark plus. The truck has 192,xxx miles. Could it be the cam position solenoid? Kinda stumped. Any help is appreciated. Thanks.