i have a bailys dv there is a nut coming off the top of it with a pipe coming off it the nut is slack should this be tight and if its slack would this cause any problems

 

I think the nut allows you to rotate that vac pipe so that the vac hose for it can fit it easily - just slcken the nut, rotate the vac pipe to the optimum position and connect it to the inlet manifold with a length of vac hose. Then retighten nut, so pipe can't move again.

...AND/OR... it might control spring adjustment... Depending on the nut's postion, the valve will open softly or a more on/off aggressive nature. If it is adjustable, then do road tests to find the optimum positon i.e. so the motor idles smoothly, whilst the valve opens/shuts fully when off/on boost.

 

cool if it was supposed to be locked would this cause me to loos boost as i have a bit of a boost problem you could check out me other post on here it has seriosly got me beaten

 

No. Because when you're on boost, both sides of the valve are pressurised, so there is the same boost acting on both (opposing) sides of the valve, thus cancelling each other out, keeping valve closed. So i think it wont matter if it's set 'hard' or 'soft'.