I just replaced my OEM nozzles with 231,400 miles on them yesterday using new PowerPlus 357 nozzles. These nozzles offer about +10 hp / + 20 ft-lb, so it's not really a kick in the face kind of power upgrade. The engine runs smoother now both while idling and at speed. There's a little less lag in how quickly the car takes off when floored and most significantly it pulls strongly all the way up to redline. On the old injectors, the tachometer would slow down above about 2600 RPM and it would take a lot longer to gain speed above that RPM. Now, the car quickly accelerates all the way to 4000 RPM. There is also very little smoke; just a little noticable in the rearview when taking off in 1st.

Suggested replacement intervals for nozzles on TDIClub range from 50,000 - 150,000 miles. Based on this graph of average MPG per month by year, it seems to me that my fuel economy began to dwindle in Oct-2002, which is when I had 120,000 miles on the the original nozzles. I've updated my spreadsheet to include an injector nozzle replacement interval of 120,000 miles.