I must agree - stating "they run too hot" isn't very specific. Nonetheless, i have the twin prong bosch in my ML320 and it made a HUGE difference (changed at 60k) in gas mileage. I still have to pinch myself to believe how well my truck is running. Improvements all around. The old plugs were factory plugs and were in good shape when i removed them. I'll try the 4 prong bosch in my GTI 2000.

While on the subject of changing things to a high level of quality over stock...what you think of swapping the OE airfilter to a KN airfilter? Dealer stated they don't recommend as it would mislead the mass airflow sensor and therefore engine could run lean/rich. I've done this with past cars (mustang gt, toyota supra, vw gti) with notably improved performance.