I got the car back from the shop. They noticed it running considerably better after they installed the new MAF sensor and did a full reset (touch both battery terminals together for 10 minutes).
When I picked it up, it was still idling around 1000 and didn't drop revs as fast, but it's not spiking 4000 rpm at random anymore. I did a throttle reset and took out to some side roads and beat on it a bit. It still had all the power and seemed to run smoother.

I'm going to have Eurocharged retune it for me and hopefully that will balance everything out.