Hi all. Well to cut a long story short I removed my inlet manifold and had it polished up. I done all the good stuff, replaced the injector port plastic caps that sit in the inlet manifold, and replaced the injector seals as well as a new gasket of course. The problem I had was that when fitting the plastic caps to the manifold they wouldn't give any indication of when they were tight. They would keep winding down on the thread untill the top hat section would just crack. I ended up cracking 3 out of 4 they are such a bad design. So a trip down to the stealers was needed, to purchase more I have fitted them all, and sealed them using sump gasket sealer. But I am getting a hissing sound from what sounds like the 4th injector. Has anyone ellse replaced these caps. And if so what did they use to seal them in to stop any leaks? Audi workshop manaul makes no mention of any sealant to use and it states they are only torqued to 2NM. Any help would be appreciated. I'm considering getting a garage to test for boost leaks to see if its any of the vacuam pipes underneath the manifold as they are very dirty, have moved them around when the engine was at idle though and there was no drop in rev's so I think I can rule these out.