Quadruple insane stunt
From GTA III to GTA VCS, a feature that was part of the core gameplay was the game notifying and rewarding you that you had done some insane air stunt. From GTA III to San Andreas, the best stunt you can achieve is the triple insane stunt. In LCS and VCS, the quadruple insane stunt can be achieved. Based on the script from GTA III to San Andreas, it seems like quadruple insane stunts were implemented into the code but were not implemented correctly. PLPynton found and fixed that mistake and now we can achieve the impossible quadruple insane stunt.
The following is a simple guide on how to correct this mistake. It is done on an unmodified script (most importantly the HJ thread unmodified) decompiled using Sanny Builder.
GTA III
Find
$757 > 4.0
Change it to
$737 > 4
Vice City
Find
$749 > 4.0
Change it to
$729 > 4
San Andreas
Find
$1304 > 4.0
Change it to
$1292 > 4
Notes
If the option "Write opcodes" is enabled, remove the opcode. Sanny Builder can compile this without an opcode. If "Custom variable names" is enabled and you can't find the line, look at the "CustomVariables.ini" file and see what name was associated to the variable.