Zerostart tank heaters are what Frost Heater uses.
There's a current thread happening at TDI Club about them. Many people are saying to save your time and just buy the kit. I've seen a few new kits advertised for about $75.
Ave you resealed your air flaps in the heater box? My heat starts way sooner and blows way hotter since that was done.
I also have half of my radiator covered in cardboard. In a few weeks, the entire thing will be covered.
-Todd
I haven't touched much of anything. When the engine is up to temp I have great heat, it just took it a good long time last year to get it warm.
If you have the bypass like the 1.6TD, I advocate the hose heater. Easy and works very well.