Quoted from Lhyrgoif:I'm not sure its the correct guide, but its numbered as #2
https://www.pinballspareparts.com.au/mm-bg02.html
if it's the correct guide then it's located just below the entrance to the catapult (I think).
Some of their part numbers are random ones they made up unfortunately. That part is actually 01-14752.
I went through most of the PSPA ball guides and translated them to the Williams part numbers if anyone is interested.