Pulling the cap will vent it temporarily. I'm talking drill a hole in the cap. I have a post on here that shows how and where (last of the pictures I have been able to post). The vent valve, vacuum actuated, is in an impossible place to access. It IS accessible but will take hours and hours of removing stuff to get to it. It is just more practical to drill a hole. The DT300i cap looks like it was made for that hole to be where I put it. Find the pics and it will make sense. I have had ZERO start, idle, run problems since the cap was vented. Used to do the TPS/ISC RESET procedure to solve the problem but don't have to do that anymore. Do not know why reset would work anyway but it did. Dealers did not know how to solve the problem or what the cause. All that was solved here.
Karl