What cable are you using? If it only does it when you try to datalog, It may be the cable is shorting out something In the ECU. Are you sure youre hooking up the cable to the Diagnostic port correctly?
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I used to have a 420A...
'92 TSi AWD
11.8 @ 119mph 470awhp 405 ft/lb torque 30psi on E85 w/ Borg Warner S256 Turbo