I have a 1992 twin turbo and there is a really weird clattering noise when the rpm's go over 2.5k. The clattering noise only happens when the engine is under acceleration or steady throttle. If you are down shifting the noise isn't there. It is very annoying and loud. It sounds like a metal on metal noise. I have gotten under the hood to see if i could find the source but it seems to be something out of site. Does anyone know what this could possibly be?