Could this be a timing chain issue?

It could be a lot of things. Piston slap, bearing noise, timing chain, sticking lifter, wrong oil, engine heat soaking when you shut it off making the oil too thin, an accessory like the air conditioning compressor. Hope that helps! Jim

Odd that is does it at operational temperature, usually they only do it at initial start up cold, the only other reason could be the timing chain guides are badly worn and letting the chain clatter. either way if you don't get it fixed very soon you could wind up with engine components scattered all over the ground

I expect that your thirteen year old injectors are leaking and on hard starts, they're producing so much drip that you get excessive combustion that sounds like knock. Resistance to accelerate uphill is caused by the damage excess fuel has had on the catalytic converters, which are now clogged. Replace the injectors and check converter & O2 sensors. You're gonna need a mechanic for all this.