I have GTA III on my PC (bought it years ago) and its modded with Real GTA, but there's an old trainer I used o have that I can't find anywhere! I've searched for hours on end with no luck, all I find is crappy stuff that allows hotkey cheats etc, which is not what I'm looking for! The trainer I had allowed me to change the stat values and traits of vehicles, which was the best fun to be had in GTA III imo, but none of the trainers I've come across thus far seem to have this feature (the closest I found was Vehicle Spawning).

Please help me if you know where/how to find such a trainer (I have my old saved games so everything is unlocked and completed, I just want to drive 300 mp/h with a 100.000 kilo Taxi with 1/4 of normal traction again damnit)!  

did you try this one? http://grandtheftauto.filefront.com/file/GTA_3_Ultimate_Trainer_35;44282

Check gamecopyworld.

 The most widespread one, but it only contains character stats and hotkey cheats and other rubbish... Idid find one similar to the old one but it was very clumsily put together and userfriendly like thistle.