I don't know what brand, but I had it done by a highly recommended mechanic that has done a lot of service for me in the past. I'm sure he knew what he was doing, and they always use OEM parts in their shop. The problem that sent me to get new plugs has not returned. What brings me here is an all new kind of monster.
Actually, come to think of it... I say "all new", but when I had trouble with my transmission speed sensor last year, it threw the same emission code a couple times then as well, but no related performance issues. It wasn't exactly a priority so I ignored it and it went away-cheapest fix, however temporary, I've ever had the pleasure of doing myself. XD
I'll just add now that it seems highly unlikely to be a bad catalytic converter, a problem I came across with my first Pontiac. Currently, I only have the one code that I mentioned - Evap Emissions System P0441 - which on it's own suggests something related to the fuel system. Also, when the car 'misbehaves' it's almost exclusively during the acts of speeding up or slowing down.
Overall it doesn't 'feel' like a bad CAT, especially without any directly related codes. I still drive on the highway every day for work and the ride stays pretty steady with the cruise on, if that means anything. I'm unfamiliar with the fuel system and unaware of which valves and sensors are involved from tank door to cylinders and I'd rather not spend$150 on a manual that may or may not have the answers I need... so I only have theories, like maybe a vacuum leak or something in the tank.. and I'd be extremely grateful for advice from a mechanic that really knows these cars, if possible.
Thank you again for your response!