Undy Dave what would happen if you charged the manifold with Freon? you have a sniffer like mine that will pick up very small leaks and the dye will leave a stain wheres its coming through?? Brain farting, Pat's not helping yet!!!
Rick L. Ps if this doesn't show anything, do the block the same way if you can get a good seal.
By the way Pat like the dentist office for his fix.