Injector Problem??

[Big_H316]

It's been a while since I've posted because I haven't had my truck for a whole month because someone decided to let their livestock runamuck and guess who was cruising down that stretch of highway on that sorry January 1st night?? Sorry thing trashed the entire front of my 03. Tie-rods, front tires, both fenders, the hood, fender wells, radiator, intercooler, trannycooler, fan, fan-clutch, headlights...you get the picture....not a pretty one!! It was all destroyed in a split second, but hey, my sorry luck, it wasn't even totaled. That was the most depressing part of it for me. But onto my question. The engine has 160,000 miles on it and I've asked this question before and never really got a good answer. Not all the time but sometimes the truck, at idle, would drop in rpm's and KNOCK AND CLATTER REAL REAL BAD and then it would race up to around 1500 rpms and start the process all over again. The whole this is going on it is chugging black smoke out the tail pipe. The last time this happened I had it in the drive so I popped the hood and cracked the forward most injector line and the engine smoothed out and idled fine. Tightened it back and it went crazy again. Dealership has looked at four times already and always tells me "there's nothing wrong with it" because everytime the get the truck it runs fine. They flashed the ecm on it and more times than not it will idle down to around 1200 and stick there. If I slip the tranny in gear and ease out one the clutch it will go down to normal idle.

Is there ANYONE who has experienced any of this?? Please help me?