anyone fitted AP50 cruise control to turbo-diesel?

Don't you mean intake manifold???

I thought it was exhaust, could be wrong, either way, my cruise control works just fine

Nah mate, it has got nothing to do with fuel type, "problem" is turbo. With normally aspirated engines engine trys to suck in as much air as it needs, but air is restricted by air filter, size of the manifold etc. etc. so you have vacuum being created, bigger demand for air than avaiable you can describe it that way. For turbo engines, turbo actually pumps air in to inlet manifold and creates positive pressure where normally aspirated cars would need to suck it on their own, since there is positive pressure, there is no vacuum!!! Since most diesels now days are turbo, most of them need separate vacuum pump! I personally don't like vacuum operated system, if the car is a carby one and you get in to problems with vacuum oooooohhhh, I'm just sick of it!!!

yep, decided to get an autoelectrician to fit it anyway despite him insisting that it wouldn't work very well. Anyway, he was very surprised with the result - the AP50 works great!