"O" series advice: please

[jaycey001]

Hello
Following my previous post i have cleaned the crank case breather which was located in the oil filler cap, (is this right?) but all seemed o.k.!
I always have to run the engine on premium unleaded otherwise it will run on and always need the choke to start it when cold.
Yesterday i was driving at 50mpg and then had to stop at traffic lights; i noticed a dark grey smoke from the exhaust which i have not seen before. It cleared after a few minutes. I also get light grey smoke from the exhaust throughout a journey, even after a 100mile trip. But i have never had to top up the coolant. the van seems to accelerate well in the first 20min of the journey but once the engine is hot it seems as if the initial acceleration between 0-20mph is reduced, quite considerably! there is also a slight stutter when idling every 30-40seconds, both in drive and neutral.
I feel something is not quite right, but at this stage it is so slight i doubt any garage would detect it, (you know when you just know the feel on your own car)
Any suggestions on what the problem could be?
The van has electronic ignition and an electronic pressure regulated fuel pump (Huco) it is 2.0 litre auto in a 1984 Sherpa van. the fuel tank has recently been cleaned out and the carb cleaned (but not striped and rebuilt)
I will be driving around 150miles on Sunday and would like to, at least have an idea of what to expect.
Many thanks
James

[JPB]

By Premium, I take it you mean the bog-standard, 95RON stuff. Perhaps you would benefit by using Super (97-99RON depending on which brand you buy), the direct equivalent - but without the lead that you don't need anyway - of the 4* and 5* fuels of times gone by.
That won't solve a problem if one exists here, but my feeling is that this smoke you're seeing may be connected with your recent fuel system cleaning exercise.
What did you use to flush the tank and the line? Could be that the cleaning material has dislodged some old paint from the tank and/or lacquer that's built up in the line over a few years, in that case, expect the smoke to disappear after you've run the cleaner all through. Better a little smoke than loose flakes of the stuff blocking the line.

a slight stutter when idling every 30-40seconds, both in drive and neutral.

Fuel supply? Could the pump you fitted have captured some of the crud that flushing the system would have dislodged, maybe the regulated gubbins on the pump need to be checked and adjusted? I'd take the filter out of the device and make sure that it's clean too.