I am having the same problem but when I took that manifold off there weren't any butterfly valves. The casting marks for the rod that hold the butterfly valves wasn't even there! I don't know what the problem is.
2005 Mustang GT; MMR Pro Street 900 short block, T-76 Garret Turbo, 55mm TIAL waste gate, HKS Blow off valve, GReddy Boost controller. 60Lb injectors, Hotter coils with solid core, Brisk racing plugs, BBK Equal length headers, Borla Exhaust. There is also an Aafco dual core radiator, aluminum drive shaft, McCloud Clutch (never buy it, it's too heavy), and Eibach Pro Street Coil overs. 716 RWTQ and 656 RWHP on 19.7 Lbs of boost on a mustang dyno!