Help! What am I missing? S5 NA vacuum leak
 

I am working on a S5 NA and could use some help. So the car ran fine and idled great but was leaking oil pretty badly. Oil injector feed lines were leaking. No problem, removed the UIM and replaced all 4 lines. Replaced the gaskets and put it back together and now the car has a severe vacuum leak and will not idle at all. Pulled it back apart thinking i must have left a vacuum hose off....nope did not see anything out of place. So i noticed the injector seals were old and hard so I replaced them all. Still same issue and won't idle. Spray propane under upper manifold and will smooth out and idle for a few seconds. So i am thinking maybe the lower manifold gasket is some how leaking so I pull it all down again and replace the lower intake gasket with the updated metal gasket from Mazda. Still same issue. Anyone have any ideas? Any help would be greatly appreciated as I am scratching my head on this one.

Forgot to add it is a 90 model with low miles and completely stock if that helps.

I just went through this whole ordeal as well. Take everything apart, check your hoses and connections and specially the ones to the IACV. It tool me two times to get it all good.
Good luck.

agreed, go back through it and check, recheck then check again. nothing worse than getting it back together and having an issue like this.

also if anything is vacuum capped replace the cap. i once had a super brittle cap cause a vacuum leak

I'm new to rotaries but couldn't this be a tps issue if you were removing you upper intake manifold?

I removed mine to clean up my fuel system when my primary injectors were clogged and it caused my s5 to idle all over the place.

doubt its the TPS sensor. thats just a potentiometer that says this angle=that voltage. youd have to adjust it to screw it up.