Turbo Conversion Gone Bad - MAC 11C Troubleshooting

[blarson at Zeiss.com]

All,

My friend and I need help troubleshooting an error on the MAC 11 in his
80tq.  Background: The car is a 1990 Audi 80Q converted with a 1987 MC
motor and MAC 11C ECU.  The code light is hooked up to the brown connector
under the dash of the 80.  When I pull codes it comes back with 4444 (no
faults).

Problem:  The fault light comes on as soon as you start cranking the motor
and stays on when running.  As a result the computer is running in limp
mode (low boost).

Troubleshooting to date:
1) Swapped knock sensors, check continuity to ECU and started car with
knock sensor out of block.  No effect.
2) Verified function and readings of air temp sensor, coolant temp sensors
to ECU.  Correct resistance and readings at ECU.
3) Swapped MAC 11 with another known good ECU.  No effect.
4) Checked WOT switch resistance readings.  PASS.  Note this unit what
taken apart and resoldered as well.
5) Shorted terminals 2 & 3 at WOT to make wastegate frequency valve run.
PASS.

Any suggestions of what I should try next?  What signals is the MAC 11
looking for when cranking the motor?  It is getting some reading it doesn't
like from some sensor when cranking.  Could it be a bad ground somewhere?

If you can think of anything else I should try it would be greatly
appreciated.

Additional question: With a turbo conversion is it necessary to hook up the
wires to the brake light switch and multifunction temp sensor (over temp
input).  Other guys I know have not hooked these wires up.

Thanks