Sudden Engine Knock

[GMO]

1999 7.3L turbo powerstroke diesel, 166,500 miles. New transmission less than 10,000 miles ago. Was sitting in the truck at idle with my foot on the brake. Engine began to shudder and knock like it was misfiring, no CEL. It smoothed out and I was able to drive it home with no additional problems, except for a definite knock that increases/decreases with engine speed that wasn't there before. Took it to the stealer for diagnosis. $300+ later was told the problem could be internal: ACTUAL DIAGNOSIS FROM DEALER: "Checked oil level, ok, no codes; noise coming from the L/side of the engine; killed each cylinder, noise got softer on #4; relative compression passed; noise is internal engine, possible wrist pin". I suspect injector problem, but can not confirm with home tools. Any Ideas?