I did the speedrun thing and made it through the heat door after the first boss. I'm supposed to be trying to find the Foam Gun early, but I have no way of getting there because I'm completely stuck. I can't even go to any of the doors on the right in the big room.
I haven't played the game in a couple years, but if you're doing a speedrun, have a watch of this:
Should show you the optimal route. Maybe you're stuck at the part where you have to get that foam spider to actually open a door for you by tricking him into shooting the switch.. in that dark room where the soldiers have flashlights. Anyway, hope this helps.