I also had had to replace knock sensors and after reading man forums, I learned that any brand other than AC Delco might work for a very short time, but would end up giving you problems again. When doing knock sensors GM sensors are the only ones compstable. On the question of TIMING, a worn chain and prob sprockets to, can cause your timing to be off from about 3 - 6 degrees. This will cause a rougher idle, possible loss of power, loss of gas mileage, and the clatter noise you refer to. Mine started the noise recently when at operating temp, but quiet when cold. I am thinking that is because of expansion and contraction, everything is a little tighter when it’s cold. I haven’t had much loss of power but I am down to 11mpg avg which is quite a bit low. But if u decide to tackle that job, it would be smart to also do oil pump, pick up tube, and screen while your at it. Since it is all right there and you wouldn’t want to tear all that down again later on. Water pump to if u haven’t already. Water pump gaskets at the least.