I guess it can’t rule it out, though the spark plugs are literally brand new and are OEM. Any insight on what I should replace
I did not think the car had one, but I just looked one of the common parts websites and it indicates there is an “in pump filter” in the tank; maybe that’s it! Also, regarding cruise control, I do not have this issue when it’s turned on.
A hunch: the throttle plate is sticking/vibrating against the gummed up walls of the throttle. (Going downhill, you need little or no throttle opening.) The cruise control holds the throttle plate just a tad farther from the throttle wall, enough to keep it from sticking at all.