They probably using HDD Loader, if you wanna see a turboing player... you should see they running with you in the same place, If that player running like a ghost rider and so fast like a vampire, they probably turbo it.
Yeah, I had seen some guys like that. I do not have joy to play like that. I can not do nothing to get the key items, when playing with "turbores". I can just follow he/she/them and help with some shots.
Yes me too, it suck when we have a team with "turbores" player without waiting or let other player to do something because it's a Co-Op game not lonelywolf mode.
These players are not using turbo. They are using a faster loading setup which is completely allowed and any one can do using PCSX2 emulator. It is called OPL+HDD (HDL install). It requires you to enable the emulated HDD, install the game discs using HDL (HDD Loader) and NOT the in-game "HDD Install" option. Additionally there is an option in OPL under the individual game settings to enable Video Skip (though i haven't noticed it to increase speed and it does not automatically skip videos - you still need to press the button to manually skip).
Again i repeat this set-up is allowed. If you do not want players with faster loading or HDL to join your room you could specify something like "No Fast loading" or "No HDL install" etc in your room title...
If you are playing on real PS2 console i suggest using a Fat PS2 with internal HDD with games installed using HDL.ELF. You will find you waste less of your playing time on loading screens and door transitions. And it is only slightly slower than the PCSX2 setup i mentioned above.
If you are playing on PS2 console using USB drive your load times will be even x3 longer than playing from DVD, so little wonder that others will appear to already be 2 rooms away from you by the time you have finished loading. I see this all the time and have seen players who take the same time to load as i do (so i know are not turboing, i.e. using F4 on PCSX2) accused aggressively by other players of cheating with turbo use. Server lag will often add to this effect and look like players/enemies are teleporting around.
I agree though that in some places players using fast loading set-ups need to be mindful that enemies may be waiting right next to slow loading players characters because of the delay. Hellfire start is one example of this. A fastload player will already have had time to enter Boiler Room, trigger cutscene and go through the door blocked by the zombie sitting against it before very slow loading players even load into the start room. If i see anyone is still loading up in this room when i come back in then i wait and keep the zombie away from them until they do load in and start moving...
In the end it is better, if you can, to just get a faster loading set-up and avoid having to complain about others making it difficult for you...

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I have yet to witness personally any verified turbo using player, but that does not mean it doesn't happen...