The game is set to reflect the cars that did not make it into the race. There were a number of withdrawals in Monaco, Williams and Simtek only ran one car, and Sauber withdrew altogether. Unfortunately I've not created a simple way to amend this.
However, you can follow the instructions below, and basically change any zeros to ones and it will disable this tweak.
Browse to the folder:
.
..\Carsets\F1 1994 v4.2\Data\Tweaker\gp4tweak_dataopen
numcars.inireplace it with the code below and save.
; ============================================================================
; GP4 Tweaker
; Set Number of Cars per Track/Circuit
; ============================================================================
; Set cars that availables per track/circuit
; Value is in bool; 1 = available, 0 = not available
[CARS_NUMBERS_PER_TRACK]
TRACK01 = @Melbourne
TRACK02 = @Sepang
TRACK03 = @Sakhir
TRACK04 = @Imola
TRACK05 = @Barcelona
TRACK06 = @Monaco
TRACK07 = @Nurburgring
TRACK08 = @Montreal
TRACK09 = @Indianapolis
TRACK10 = @MagnyCours
TRACK11 = @Silverstone
TRACK12 = @Hockenheim
TRACK13 = @Hungaroring
TRACK14 = @Istanbul
TRACK15 = @Monza
TRACK16 = @SpaFrancorchamps
TRACK17 = @Interlagos
; aliases -------------------------------------------------------------------
; 21 -+
; 22 - + |
; Minardi1 - + | |
; Minardi2 - + | | |
; Jordan2 -+ | | | |
; Jordan1 - + | | | | |
; Toyota2 -+ | | | | | |
; Toyota1 -+ | | | | | | |
; RedBull2 -+ | | | | | | | |
; RedBull1 -+ | | | | | | | | |
; Sauber2 -+ | | | | | | | | | |
; Sauber1 -+ | | | | | | | | | | |
; Mclaren2 -+ | | | | | | | | | | | |
; Mclaren1 -+ | | | | | | | | | | | | |
; Williams2 -+ | | | | | | | | | | | | | |
; Williams1 -+ | | | | | | | | | | | | | | |
; Renault2 -+ | | | | | | | | | | | | | | | |
; Renault1 -+ | | | | | | | | | | | | | | | | |
; BAR2 -+ | | | | | | | | | | | | | | | | | |
; BAR1 -+ | | | | | | | | | | | | | | | | | | |
; Ferrari2 -+ | | | | | | | | | | | | | | | | | | | |
; Ferrari1 -+ | | | | | | | | | | | | | | | | | | | | |
; | | | | | | | | | | | | | | | | | | | | | |
Melbourne = 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
Sepang = 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
Sakhir = 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
Imola = 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
Barcelona = 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
Monaco = 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
Nurburgring = 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
Montreal = 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
Indianapolis = 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
MagnyCours = 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
Silverstone = 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
Hockenheim = 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
Hungaroring = 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
Istanbul = 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
Monza = 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
SpaFrancorchamps= 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
Interlagos = 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
; ----------------------------------------------------------------------------
; end of config
; ----------------------------------------------------------------------------