when there is no car you should try
but when you instal a new car and somehow something went wrong (game crashes) then you should resotre old car by using Vehicle mod installer
taxi is problem coz i believe you see taxis instead of the cars you have put.
ok i see....
Propably you have not good PC
like me...or you installed a bugged car.
delete the traffic load - maybe too many modded cars are about to pop up on the screen.
restore 1 car - go check game...if ok then play or add another different car
if after 1 restoration game still sux then try restore another original car
if you use ICEnhancer and ENB and you have not powerful PC such situasions may occur (with modded cars, high graphic, enb...i can play with 11 cars...more mean crashes)