Greig,
Before you start pulling things apart again to check timing, you mentioned the ECU has no power.
Where did you measure this from ?
agree with Simon, if you have the apexi PFC you will not get anything from the diag port. but you mentioned you tried several ECU so assume one was an OE one, so you should get something (although MY99 are on the verge of the introduction of OBDII diagnostics and I have heard conflicting reports as to whether they work).
The Diagnostic Tool ECU Explorer should connect to the OE ECU though if you have an OBD cable for youy lappy
http://code.google.com/p/ecuexplorer...25.exe&can=2&q=