I had this on my G - there's a t-piece off the drivers side (left side) manifold vacuum line which broke off - the t goes into the vacuum storage canister for the brakes (which were rubbish until I found this out).

take the left side engine cover off, then follow the manifold feed pipe down until you find the T- you'll be able to feel if its broken or not, but there's minimal room to see it.

I had to take out the pollution canister to fix it, and it's a cursed metric tee so it was tough to get hold of one - I ended up with a straight-through irrigation fitting for a week which worked fine (just no emergency vaccum storage).

There's a whole load of vacuum pipes on the left side, so you may just want to take the cover off and follow them around to make sure nothing's dropped off.

PM me if you need more info.