Find the line that starts with
420, 	taxi, 		taxi, 		car, 		TAXI, 		TAXI, 
Replace found line with
420, 	taxi, 		taxi, 		car, 		TAXI, 		TAXI, 		null,	taxi,		10, 	0,	1f10,		-1, 0.7, 0.7,		0

In file [Game folder]\data\handling.cfg
Find the line that starts with
TAXI 
Replace found line with
TAXI 1450.0 4056.4 2.2 0.0 0.3 -0.25 75 0.80 0.75 0.45 5 180.0 19.0 10.0 F P 9.1 0.60 0 35.0 1.4 0.1 0.0 0.25 -0.15 0.54 0.0 0.2 0.51 20000 0 200000 0 1 0

In file [Game folder]\data\carcols.dat
Find the line that starts with
taxi, 
Replace found line with
taxi, 1,0, 1,1

In file [Game folder]\data\carmods.dat
Find the line that starts with
taxi, 
Replace found line with
taxi, nto_b_l, nto_b_s, nto_b_tw