Hi can anyone help.

I have noticed this pipe has come off a couple of times now, what does it do and does it need to be on as the car seems to run better with it off?

Advice please

Cheers.

 

It is a vaccuum line. I'm not sure what that particular line's purpose is, but I'm sure it should stay connected. If it is coming off, then you either need to clamp it, or figure out what is pulling on it and why. Looking at the picture, it looks like the hose is pushed onto one pipe end more than the other. Maybe centering the hose up would solve the problem.

 

Thanks gernby I'll stick it back on in the morning and reset the ECU and see how it runs.

 

That hose (or pipe as you called it) is part of a very complicated and extensive system called the "Pulsed Secondary Air Injection System". This is part of the car's emissions control system and has to do with controlling the time and duration that air is pumped into the exhaust manifold to help the cat clean up the exhaust after a cold start.
Those who have installed cold air intakes have commonly gotten this line crossed with the one next to it, resulting in a Check Engine Light. If this line were to be kept off that fitting, it would take anywhere from a few hours to a few days for the CEL to come on. The car can run in this condition but it would not be emissions friendly.