240D Hard Idle and almost dying out

[JordaanDMC-12]

Hey everyone, I've recently been having a hard idle problem with my 1983 240D. The problem is, it will be idling fine and then it gets rougher and rougher and rougher to where it feels as if its going to die out. It got to a point to where I had to keep shifting into neutral and revving it to keep it going.

I took it in and my mechanic told me it was the piece where the hand pump is when you change a fuel filter, it was leaking Diesel and he said it was sucking in air and this was the problem. So he had it all weekend and I got her back yesterday, all of yesterday she was fine except for at night when I got a hint of it coming back. Cranked her up this morning and low and behold it was the same nightmare all over again. I did a few pumps on the fuel hand pump and fiddled with the idle to see if I could get any results.

It's not doing it now but the idle is still kind of hard. I have no idea what to look for. I'm guessing it still is getting air somehow but this is just a guess. I checked all the hoses and their not leaking. I don't know if this is vacuum related or the engine. The bigger fuel filter was changed 5 months ago and the smaller one was changed this weekend with the "repair" so I don't think that could be it. The vacuum pump was replaced about 3 months ago also.