Re: 164 24v Super erratic running
I probably won't be the only one to mention it, but it's possible that the cam belt has slipped a tooth or two on one of the camshaft pulleys.
My old 164 felt exactly the same as you describe.
I took mine to the garage initially to check for a faulty plug or HT issue, but after a compresion test, they discovered that a pulley on the rear bank of cylinders was out of adjustment.
They said that the belt had jumped two teeth (surprising, considering that the engine's top end had been rebuilt not that long before I bought it!) but also mentioned that they'd seen the same thing several times before and with the same pulley!
It could be that your problem is something entirely different, but it's worth getting the timing checked before you start throwing money at various other components.
"Looking through the knothole in Granny's wooden leg"