The other day my friend's '95 turbo DSM died on us, I need some help diagnosing this problem...

The car was making this loud sort of Knocking sound. It didn't really sound like engine knock, but more like a clapping sound (intake leak?).
It was coming from the center of the engine bay, around where the manifold and head meet.

I thought it may be a intake manifold gasket leak, because we drove it to a shop, and on the way the sound got louder and the car would not hold an idle without revving.

My friend brought up that he could have fried a piston, but I didn't think a blown piston would make the car act like that.

The shop was closed Sat. afternoon, but he is having them look it over Monday.
Any comments/suggestions are welcome, and if you have had this problem before I would REALLY appreciate some help.

Thanks

There are many things it could be. But to rule out the real bad ones, do these tests. Pull the upper timing belt cover off so you can see the belt/cam gears. Crank the engine and make sure both cams turn with the motor. If they dont he lost a tbelt and has some bent valves, but the motor is most likely fine. If that all seems normal, do a compression test. If that fails (say, less than 100 in any or all cylinders), the belt may have skipped some teeth and bent some valves even though the belt itself appears to be fine. If the belt is still good and has good tension, and compression is good, then you guys are free to relax, and look into the smaller things. But I have to tell you, I'm not too optomistic ;) Good luck