Weird problem

Sounds clogged cats. Being you are in Cali sucks because you can't just put on an off road pipe and go on your way. Try the plugs and see what happens but I'm betting you will have to replace the cats. Try classifieds to find someone selling a stock H. A lot cheaper than paying a shop to replace.

Plugs are fairly easy to change. Make sure the engine is cold when you do. Likely you don't have a torque wrench if you are new to auto maintenance but getting them tight then making an extra turn on the socket wrench should suffice. After a few hundred miles it would pay to give them another whirl with the wrench to make sure. The gap is listed on the hood sticker in case you forget or want reference. The right tools are a plus. Should have a few extensions and a swivel...3/8 drive socket wrench would be fine. Most Sears you can buy a pretty decent set for about 50-75 bucks.