My 1989 Firebird had factory VATS (Pass-Key) - do I need to do anything with the old system when swapping in a 2001 LS1 with a standalone harness and 2001 PCM?

Here is what the documentation says. Each point links to its source; details depend on your exact computer, harness and transmission.

Computer and tune

• In HP Tuners VCM Editor, VATS is disabled by going to the System tab, then Security, setting VATS Control to 'None', saving the file, and performing a Write Entire. A VATS disable is required on swapped powertrains so the engine starts and runs; it is not required when tuning a stock vehicle. (HP Tuners (official channel))

Harness and power

• 0411 PCM (GM service #9354896 or 12200411); 1999-2007 Vortec DBC (LM4/LM7/LQ4/LQ9/L33/L59); T56 or non-electronic automatic: Harness uses GM Delphi connectors and cross-linked 600 V wire. (PSI Conversion)
• 0411 PCM (GM service #9354896 or 12200411); 1999-2007 Vortec DBC (LM4/LM7/LQ4/LQ9/L33/L59); T56 or non-electronic automatic: VATS must be removed from the PCM or the engine will not start. (PSI Conversion)
• Gen III PCM; Aeroflow AF49-1505; LS1/LS6; DBC; 4L60E/4L80E: VATS must be removed or the PCM will prevent starting. (Aeroflow Performance)

Confirm against the instructions for your exact parts before wiring. More: Computer and tune in our tuning guide.