I can try to explain, though I'm afraid there's no guarantee that my specific case will apply to your game - and it may not even be possible at all.
I assume it depends a bit on how/if the developers actually added in a functionality to 'slow down' gameplay... like games that have an in-game feature to slow down time temporarily, obviously have the 'function' - but - I don't know a whole lot about all those things actually.
Anyway though, what I did was - I actually followed this guide, to make a widescreen patch:
https://forums.pcsx2.net/Thread-Guide-Cr...#pid215566
And in the process of finding which 'address' had an effect on the screen/camera - I came across the game speed one.
(Mind you looking for the right value can be a lot of fun on its own - like I extended draw distance, shrunk my character - increased enemy damage modifiers, and extended agro range - so all of a sudden level 1 monsters came from nowhere and one-shot me xD )
In my case, the default value for the game speed was 3F800000 in Hexadecimal (or 1 in float ), as he suggests trying out first in the guide as well.
and I just calculated that, if 1 (float) is 25 fps, which is default game speed, then 2 (float, or 40000000 hexadecimal) is likely to be 50 fps - and I tried to do that, and see if the game would run 'properly with 200% game speed, which it then did.
(note: to convert between float and hexadecimal you can use this site:
https://gregstoll.dyndns.org/~gregstoll/floattohex/ )
If you intend to give it a try - personally I used Cheat Engine, as suggested in the guide as well. Getting the program however is a bit - well, shady, I find personally.... Go to:
https://cheatengine.org/ - click Downloads - then look for the line that says "For those that want to have Cheat engine Setup without any extra software recomendation during install, then join CE's patreon and download using this link and you'll get a clean install file, and if you wish to have the raw files without any configuration of file access permission by the setup click here. Do keep in mind that you need to add the windows app user account to the dll's else dll injection will fail in UWP apps" - download it via that Patreon link - to not have any unwanted junkware come along with it.
If your game does have a similar value, it might not be defined as 1 (float) or 3f800000 (hexadecimal) - they could have given it any value really I assume.
Oh oh - and if your game has a slow-motion function... what you can do is also "scan" for "unknown initial value" while the game is in slow motion, and scan for "changed value" once the game has returned to normal.... and then just to filter out some more things, then activate slow motion again, and scan for 'changed value' again... and perhaps a few times "unchanged value" when nothing has changed since last scan.
Oh and the 'range' to scan between, 20200000 and 21FFFFFF is a pretty good start as well, at least mine was found early in that spectrum.
If you go too far below, or too far beyond that range, you will start to mess with things not related to the emulated games, but rather PCSX2 itself (at least that happened to me when I felt adventurous D: )
But sorry, I am not very concise:
TLDR: follow linked guide - and you may just come across the right address and value
guide suggests first of all to search for hexadecimal value 3F800000 in the address range of 20200000 to 21FFFFFF - which worked for me (though it takes several tries - but yes: just follow the guide exactly, that is much better than trying to make sense of my wall of text here xD )
Edit: you can also try and request a patch, mentioning your specific version of the game, here:
https://forums.pcsx2.net/Thread-60-fps-codes