Need help, 1986 Subaru GL hatch ea81

I've had my 1986 Subaru for a couple of years, always ran fine when I drove it. A couple months ago, it started sputtering and I had to keep the rpms at 4k in second to keep it from dying.

I couldn't figure out the problem and I re did the vaccum on it, did an EGR delete (sort of) and nothing.

For some reason I started it a couple days ago and it ran totall fine and I put a full tank in it and drove it for an hour an a half around town. Messed with some vaccum lines and it sputters heavily when I accelerate like it did before and it only runs fine at 4k (warmed up of coarse) it will idle with a miss and misfires heavily with lots of backfire when coming down.

When I unplug the O2 sensor, nothing happens and I was curious if it being broken might have something to do with it.

It does have a computer and a Hitachi carb. Most vaccum lines hold pressure and the vaccum advance doesn't work.

Any help is greatly appreciated

If you have any questions about the car or anything else, please ask