I actually took it to a shop to have the idle and backfire fixed and got it back doing the same thing. Left it at the shop and told them and the next day I was told I needed a new fuel pump. Once I capped off the vac on the throttle body there was no more issue with the surging idle. I've used this shop before and I trust the owner but I'm a bit weary of some of his mechanics. The guy that worked on my car there in the past retired and I'm not super happy about that. So I'm trying to avoid taking it to the shop.