OK I tried it on one of my tracks and just by changing PITLANE=0 and it should disable the limiter speed for the pit area. It worked for me.
Make sue there is not more than one PITLANE=1 in SURFACES file.
Note: I have noticed a few car mods that I have dont slow down in the pits when PITLANE=1, so there may be car mods that slow down no mater what the settings. Not sure though.
My question is what car mod and track are you using? Try testing track with several different cars with PITLANE=0, use some of the cars that come with original game. There may be overriding features in the car mod that might control limiter speeds, not sure, cause I dont do cars.
There is nothing else in the game settings that deals with the pit limiter speeds.