Nope, it doesn't have to be, and it doesn't even have to be Tweak... Food for thought: I can easily do every track in under one (ok, make it two) seconds in any car, without modifying it in any way.
tweak is a software that increases your performance (horse power) quite a lot
and it didnt have to be tweak...just a little help from rear from some much more powerful car...for example fxr...this would make you up maybe 5 seconds only on the long straight...not that I would have tried it
Not really true. Tweak and similar apps just let you edit the vehicles to do whatever you want with them. You can make a go kart, a stock car, a dragster, anything within the limitations of LFS and the particularly editing program.