Timing Belt Replacement. I recently replaced the timing belt on my '88 325is M20 b25 (made in 3/88). It's a fairly straightforward job, although you can expect it to take you a while, especially if you haven't done anything like it before.
Porsche 928: How to Replace Timing Belt and Water Pump. It might be a little extra labor, but changing the water pump when you go to replace the timing belt in your Porsche 928 will save you a ton of time and money later on down the road.