throttle sticking???????

[jetpell]

once in a while my truck will idle rough, upon acceleration it stumbles/misses, and usually the engine will get stuck @ approx 1500 rpm and drive as though the cruise control is on. the rpms will maintain around 1500 up to a dead stop and accelerate once the brakes are released. the poor acceleration will maintain and if enough throttle is applied it will knock and ping accompanied by white smoke. the only way i can get rid of the stuck rpms is to put it in neutral I have considered injectors but once in neutral the engine revs and decels normal with no sputter, stumble, ping, or knockI have read about the APPS- but i dont think the 05's have themFCA- i think might be a problem, but i have not found any way to diagnose itI did a transmission flush and changed the solenoids attempting to fix it, it didntany other ideas or advice would be GREATLY appreciated, thank you in advance!truck is a 2005 5.9l 48RE 4x4 auto trans 168800 miles. silencer ring removed, no other mods