To answer your original question, it's an 8mm allen. Most others will br 6mm, and every once in a while you'll see a 5mm. Other than that, the only other allen type socket on the car is for the mixture adjustment, and that's a 3mm, which you'll need a t-handle, or something similarily long to reach.
-Dave '91 Jetta GTX 16V '88 Jetta GLI 16V '84 Vanagon (FOR SALE)
