Volkswagen Forum - VW Forums for Volkwagen enthusiasts - 08 Rabbit Shifting/revving/chugging problem

Hi, new to the forum and really looking for some assistance, please. I have an 08 rabbit that began revving at idle a couple of months ago. It drove and shifted perfectly fine at that time. Then, a few weeks ago, it began chugging at idle and I exhaust would let out a big puff of black smoke upon start up. It also began making a fairly audible humming noise during idle as well. I took it in and was told that it was the PCv/valve cover and gasket. So, I had those replaced as well as the air filter. It drove perfectly for about half a day after that except it was back to just the revving at idle but everything else was fine. About 2 days after we replaced that, it started chugging again but only on start up then progressively got worse and began doing it again at idle. It was off and on though and sometimes would be fine at idle and sometimes would chug, there was really no rhyme or reason to it. Then today, it suddenly stopped shifting properly. When I press on the gas, it will just rev up to 4-5000 Rpms and sometimes will shift and sometimes will not. I literally could not go over 5mph. Oddly enough, when it started doing this, the loud humming noise went away. I turned the car off and let it sit a few minutes and when turned back on, it shifted much better but still not perfectly for a few minutes then went right back to not shifting again.
The car has 130,000 miles on it if that helps.
Any insight would be appreciated!