VZ 5.7L cars going into Limp, power reduced mode is quite common and is often more than likely caused by a failing pedal. These pedals are getting harder to find in working condition and are fetching a large some of money these days as people understand their rarity.
The pedals although coming in different part numbers are easily identified by the "Blue" sticker on the sensor section. The rest of the VZ range ran the same looking pedal but the sticker on the sensor is "White". The sensor works differently and therefore the pedals can't be interchanged between the V6/6L VZ's and the 5.7L VZ's.
With so many calls on this and finally getting the time Ultimate Conversion Wiring have come up with a solution. You can purchase a Module that allows you to run the V6 and 6L pedals out of the VZ's along with also being able to run both VE and VF V6 and 6L pedals.
Link - https://www.ultimateconversionwiring.com.au/store/vz-ls1-57l-fbw-pedal-module