HI Lee welcome to PF!

Personaly I'd remove your dumpvalve it would appear its knackered.

To remove - remove dumpvalve and blank off gap in hose(usualy dumpvalve blanking plug or simply replace hose), you will then need to follow the vacume pipe(small hose) it will likely be seperated by a T pc at some point, remove T pc and vacume hose to dumpvalve.

Now ensure that the hose that was originaly tapped into with the T pc (where the T pc was) runs continueously without any leaks(you may need to replace a length of Vacume pipe)

That should see your car running a lot better!

Sounds like the Judder as swanny says could well be down to a worn bush & or wheel bearing( this may be part of your 3rd problem, although its kinda difficult to know from your description, this may fit if the noise is coming from wheel area)

If noise is coming from the engine area, it would tend to sugest that there is excesive ware on your bearings and more than likely to be bottom end related

Best of luck M8