"framedelay" only applies after I enter a vehicle since Cleo 4.3.
Tryed on different computers, currently on a netbook with a very crappy graphics card where this behavior is extremely noticable.
From ~6 FPS before entering a vehicle to ~20 FPS after entering.
Well that's just technically impossible
But when you say it only applies when you enter a vehicle, does that mean is only applies while in that vehicle, or it applies after the first vehicle you enter? If so, the problem might make more sense in some way. Perhaps it's not entering the vehicle itself, but pressing the 'Enter' key, which would still be pretty weird.
Anyway, the memory address for what 'framedelay' changes is 0x53E94C - if you can, view it in Cheat Engine to see when it's actually applied... no doubt it will be at the start of the game, which is when this script should run. Perhaps you have another mod interfering with it.