Got a Whistle but no Turbo. NEED CARB HELP

[CobraJetKid]

I have a 77 silverado with a stock 350 other than an RV cam and headers. I swapped out the Quadrajet in favor of a 2 bbl holley. Everything works fine except theres a really high pitched annoying whistle sound under load. I have a vacuum gage installed on my truck and it comes in at exactly 8" vacuum. I can't find any vacuum leaks and the truck seems to be running fine. Didn't have this problem before the carb swap so it has to be something I did but I am stumped. Anybody have any idea what could be the cause? Any help would be greatly appreciated as this phantom vacuum leak is driving me nuts.