Timing chain, escf 43

1994 saturn
1997 1.9 dohc sc series engine with ~80000 miles
I had a straight pipe coming off my car for about two weeks.
I finally found time to put a muffler on it for proper back pressure.
well, before this I was getting the electronic spark control failure error 43. I thought it was the exhaust for lack of backpressure screwin up stuff.
I put the exhaust on and I stil get the same error, and now it sounds like timing is off. It idles fine but the engine struggles when revving up. It seems the computer is doing its best to retard the timeing to make up for the chain fatigue.
maybe the time was off before, too, and the whole code 43 was actually due to knock(gasp). I replaced the knock sensor, coil pack, coil pack controller, wires.
well it seems to be getting worse and it sounds like theres random light tapping going on but in multiples.
it doesnt sound any thing like a lifter going out unless they all failed at once.
the oil only has 1000 miles on it and it doesnt leak it or burn it.
sounds like my timing chain is getting stretched or something?
it basically sounds like someone put a handfull of gravel in a jar and started turning it.
the sound comes from around the timing chain but you can feel from all over the valve cover.


thanx guys