Q: Rough idling of engine with check engine light on

All the car components were functioning properly of course with lots of oil leaks from various gaskets without any warning lights coming on. First time it has ever done this, I changed the valve cover gaskets, alternator bracket gasket, upper and lower timing chain cover gaskets, spark plugs and coils, and all O rings involved in replacing the above. Had to drop the sub frame in order to remove the upper oil pan to change the lower timing chain gasket. I washed and cleaned all the components doing the above work with Mineral Spirits carefully and everything is immaculately clean. Changed one engine mount, tension struts, wishbone, swing bar and dynamic drive bar in order to have all new ball joints (unrelated to check engine light). When I put everything back properly, started the car and the check engine light came on with the engine idling rough. I had a warning light for ("Driver restraint system fault!" Belt tensioner or belt-force limiter fault) after above the passenger side has it

My car has 140000 miles.
My car has an automatic transmission.