To simulate that the turbo actually did spool up add, if possible, an extra small percentage to the original power of the until you let go of the throttle or reach speeds where you would have the same performance.
A better way would be to just pin the turbo. There’s a native for that, which the script actually uses.
The script does set the pressure(?) to 25, though the game will just clip it back to 1.0 unless some patching is done.
A nice way to integrate the two systems would be to have an instance just being the 2-step rev limiter thingaloo that just cuts the throttle to regulate the RPM, and a separate instance that monitors the actual throttle position and does the pops and bangs (and setting the turbo pressure) in response to the throttle change.
The patch to disable the turbo limit can probably be integrated in FiveM itself and exposed as a native or something, not sure how the thing (FiveM) works.
When done it kinda unlocks the full potential of the turbo (e.g. a more meaningful power increase), as (hardcoded) at full (1.0) boost the turbo only adds 10% of the engine power, so you can more accurately simulate real engines (e.g. an rb26 doing 160kW, the rb26dett doing 235kW, so you use something like 0.3 fDriveForce as base and use 4.6 as boost, which adds the 46% power figure) - with these numbers an anti-lag in gta actually does add value (and brings down lap times).
But hey, racing servers are still nonexistant, “drift” servers use ridiculous handlings and there’s only RP junk around, so why bother with it all. Just give em pops and bangs and most of the player base is more than happy.