if the central locking is playing up then it's almost certainly the module in the drivers door lock that controls the rest of the locks

as for the noise from the inlet manifold, that'll be the swirl flaps breaking up, i wouldn't drive it anymore until you get them fixed, new manifold is about £250 or you can follow the instructions in this thread here

http://www.talkford.com/topic/97564-...raphic-detail/

if they fail, you will be looking at a new engine