[xtremech]

I agree that the valve guide and the exhaust guides are in need of replacement. The fact of the matter is that the exhaust stem to guide clearance that the factory calls for "new" is considered wiped-out, in comparison to what tolerances can be held with current materials and honing techniques.
One of the issues I have had in the past is that most any valve guide that is available for a 911 is already to big on the inner diameter even before installation. So... after the install, you hone it straight...and now you have a "new" wiped-out valve guide. I have all of my valve guides made with a .351 I.D so the clearance can actually be set properly. Remember, 70% of the heat in the valve is transferred back to the head through valve seat contact. Bad guide..bad seat contact...well, you know what happens next. See if you can maintain exhaust @ .0016---.0018 max on the clearance and you valve job will thank you for it.
(BTW.... Very accurate info Matt)

It has been a while since my last visit...good to be back.