83 Euro SC Start Intermittent

[time260]

I really need help here:

Problem: all of a sudden popped, my 911 "sometimes":
1. starts OK
2. starter clicks - does NOT turn engine, or
3. now, no starter click

Findings and done so far:

a. battery checked 12.48V with nothing running, when engine running 13.78v (alternator good). Headlight dims when ignition turn to start.
b. just replaced the Ignition Switch - Electrical Portion today - thought this is the culprit.
c. changed starter to hi torq 4 weeks ago, shotgun troubleshooting that cost me $150 - problem started even before this starter was installed.
d. Fuel pump replaced 3 weeks ago - another victim of shotgun T/S
e. Fuel pump relay replaced $15
f. Body ground wire on tranny & body checked. As well, Negative post ground - good connection on both.
g. Seems like every time I disconnect an electrical component i.e. battery post, the ignition switch electrical it starts right off - not all the time though.
h. 'sometimes' it starts oK - cold or hot.
i. checked AAV - plunger plate on half moon and not stuck. No hammer tapping on this one.

Calling all Porsche 911 Gurus: given the above, what is the problem with my car?