Another alternative is to apply some light oil such as 3 in 1 or even a squirt of WD40 to every pipe union. If air is being sucked in at any point, the oil will be sucked in as well and temporarily stop the whistle..

Doug
2011 Plus 4 in Rich Maroon

1972 750 “ComDom” sprinter
1958 Triton 650
1992 Triumph Trophy 900