Car that is never installed is spawning

3 weeks ago, I was looking for some new ELS cars. I found one and attempted to install it. I installed it in the FBI slot turned on els for the slot and went into the game. Everytime I attempted to spawn the car it wouldn't work (the game would crash). I figured the model was corrupted as I found it from and unreliable modding site. I then found a different vehicle from the LCPDFR site and attempted to override the previous car. When I went back into the game and tried to spawn the FBI slot, the new car wouldn't spawn either and crashed. I was puzzled. So I proceeded to find another vehicle and replaced it into another slot (polpatriot). When I went into the game, the car spawned in that spot. Immediately after, I tried once again to spawn the FBI car. It failed again. I replaced the vehicles.img with a original one, but everytime I tried spawning an FBI vehicle, even the original one, the game would crash. Feeling defeated, I reinstalled all of GTA 4. I then proceeded to find one vehicle model and stay away from the FBI slot and installed it in the polpatriot slot. When I went into the game, I spawned the polpatriot and continued to play for quite some time. Later on, just because I was bored, I decided to spawn the FBI slot hoping to get the original FBI car. With amazement, the car that caused this entire problem spawned. I was confused because I never reinstalled this car and everything was set to original except for the car I put into the polpatriot slot. I exited the game and went to Open IV. When I clicked on the FBI slot, it showed the original FBI car, but for some reason the car from the very beginning spawns from nowhere.

My question, after the long story, is how do I get rid of this car? Like I said, I have already reinstalled the game but somehow, now of course, it spawns. Thank you for your help!