I had my fiance fire up the 87 GN today. It has a brand new engine in it (less than 300 miles). It started to screech a bit. Loud as heck... it sounds low and front. Not a knock or tick at all in the least... Heres what I know... Good clean oil, no metal to be seen... Belt off it does it as well.. It does not happen all the time....It seems to stumble the engine.... Brand new turbo because I thought the turbo was the issue...It is very loud when it does it...The car idles like a champ and starts up just fine. Any ideas will be much appreciated... I may not be able to respond right away due to health reasons but I will check back. Thanks!