Hi,
I had his same problem with my 1.6s 8v (1998 R) Golf (MK4). I constantly kept changing my spark plugs but within 7 days the problem would re-occur. I then bought some new Spark Leads (Euro Car Parts) which cost me around £20-25 GBP and the problem was solved. Try this, its the cheapest way. I have heard of many problems with the coil packs but this worked for me.
Hope this helps
P
Paresh
January 2008