Had a 1973 Caddy Fleetwood intended for California, but got lost in Wisconsin with a secondary air pump, this pumped air into the catalytic converter to assure combustion of unburnt fuel.
Anything that injects air into the engine is a supercharger or a turbine. Common cause of a misfire is water in the gas, spark plug not firing, or a plugged fuel injector. Worse case is an intake or exhaust valve not closing, like to do compression test first, saves a lot of wasted time. And is very possible with 180K miles on a vehicle.
Use to be real easy on a 70's V-8 engine with overhead valves, you have two heads with overhead cams, that is a lot of stuff to remove but see you have a timing chain and not a belt. Could use spockets to take up the play, yours uses friction arm that wear.
Another engine wrecker is paying for E10 and getting E1 or E2, low octane fuel combusts when the piston by vehicle inertia is going up. E10 is NOT a homogeneous fuel and by all means, should be outlawed, but have crooks running this country.