You can use Stripper to remove the trigger events for the onslaughts.
I did this for Death Toll L4D2 the second to last map that has a gauntlet run to the safe room.
It works great and you can do any map once you learn the tricks.
With Stripper you create text files with the map name and put in commands to add / remove / modify the map entities which are basically most everything in the map besides the environment and walls including the triggers for the gauntlet runs.
What I did was use Stripper to turn off the trigger that starts the script for the gauntlet run.
To run Stripper you need to first install Metamod.
The steps are install Metamod and Stripper and make sure Stripper is running. Go in game join the map and do a stripper_dump to get a file of all the map entities. Look through that file to find the trigger entities and then create a cfg text file that has the stripper commands to remove them.
Here are the steps start to finish how I did this for Death Toll second to last map which actually has the file name c10m4_mainstreet.bsp.
1) On your server install Metamod
Get the latest by clicking the icons at the top for Windows or Linux or Mac
The zip file will have one folder in it addons.
Put all of the files and folders in addons in the zip into your
Keeping the structure in the zip file
2) Install Stripper
The latest one for Windows is
The zip file will agin have one folder addons.
Put everything in that addons into your addons keeping the folder structure in it.
3) Start your server and go to the console and type
You should see that stripper is running.
I have other things running. All you need to see is that Stripper is definitely running on your server.
Listing 5 plugins:
 SourceMod (220.127.116.1110) by AlliedModders LLC
 Stripper (1.2.2) by BAILOPAN
 CS Tools (18.104.22.16810) by AlliedModders LLC
 SDK Tools (22.214.171.12410) by AlliedModders LLC
 SDK Hooks (126.96.36.19910) by AlliedModders LLC
4) Get a list of all the entities for the map you want to disable the gauntlet run.
I already did Death Toll so let me show you exactly how I did that one.
First make sure your console is enabled.
In l4d main screen go to Options / Keyboard/Mouse / Allow Developer Console and make sure it is enabled.
Start L4d and join the map. In this case it was the second to last map in the Death Toll campaign.
Once in the game go to the console by pressing the tilde key, it is under the esc key.
Once in the console type status and hit enter
hostname: Austin - Server Owner
version : 188.8.131.52 8267 insecure
udp/ip : 10.10.10.110:27015 [ public n/a ]
os : Windows Listen
map : c10m4_mainstreet at ( -3093, 105, 390 )
players : 1 humans, 0 bots (4 max) (not hibernating) (unreserved)
# userid name uniqueid connected ping loss state rate adr
# 2 1 "Austin - Server Owner" STEAM_1:0:2555958 00
6 40 0 active 30000 loopback
# 3 "Louis" BOT active
# 4 "Francis" BOT active
# 5 "Bill" BOT active
Notice the actual physical map file name is
Now in the console type
It will look like nothing happened. This command for some reason doesn’t give any feedback but it should have created this file on your server
Open that file and search for
5) Here is where it gets tricky.
To disable the gauntlet I figured out the OnPressed and OnTrigger that starts the onslaught script "director BeginScript c10m4_onslaught 7 -1" and I created a stripper file with the commands to “Strip” them out of the map.
Here is the Stripper file and it goes into
; Austin - Remove the hoard from the gauntlet run to the safe room.
"OnPressed" "onslaught1 GenerateGameEvent 8 -1"
"OnPressed" "director EndScript 0 -1"
"OnTrigger" "director BeginScript c10m4_onslaught 7 -1"
The effect this has is when you get to the forklift by the barber shop sign and press it you hear the sounds and see the events as if the onslaught is running / going to run but you never get a hoard. The ramp drops down and you can continue on. Getting to the safe room from here is tough enough without the hoard!
To do other maps follow these same steps and create a Stripper file for them.
If you try to do one and get stuck post a request for help in the stripper forum (the first link in this post) and I or someone else might help you.