Alright, ran it through and thanks to your prodding found another process in the script that i needed to wrap into one transaction. However, disabling autocommit and committing manually versus wrapping in begin/end doesn't make any noticeable difference:

Autocommit off:
the code took:176 wallclock secs (106.80 usr + 26.13 sys = 132.92 CPU)

Begin+End:
the code took:180 wallclock secs (108.42 usr + 25.98 sys = 134.41 CPU)
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