What would cause a "diesel" sounding engine

[ps2cho]

I'd say my '88 300TE has progressively got worse in regards to its normal engine sound over the last year. It sounds like a diesel, but really scaled down. It's not loud at all, but when you open the hood you can hear its just not too happy.

What could cause it to be doing this?

I know my tensioner is fine so its not that. Could I have a bad lifter at 97k miles? Could that cause a small rough idle?

There is also a fast "ticking" at the back of the engine, that I hoped would disappear after I did my rebuild, but it did not. Could it all be associated?

Thanks,