I'm no mechanic, but been working on my vehicles since 1957. I replaced the drivers side turbo last year and it's still going strong so I guess DIY is my strong point. To the point: My chain began rattling two years ago and I've found mostly it's oil starvation when starting up. Yes I've been lucky but but a $3000 chain replacement versus used engine is a chance I'm willing to take. it appears the oil pump just doesn't do the job on startup, doesn't reach the chain fast enough. Most days I start remotely and it seems the pump jumps into action right away, and startup is as normal as a new truck. I read about new more powerful oil pumps so I might attempt an install.