Put the throttle body back on
This bizarrely complicated mess of plumbing is all for the brake vacuum, and oddly it just flaps about, which causes the bottom joint to fail and allow air past the throttle body which will cause misfires and poor running. The original one was quite badly perished at the bottom.
I had a spare set of pipes so put those on instead and gave the bottom joint some extra support with some adhesive-lined heatshrink
Then drilled a hole in the upper part of the intake tube (which is mostly solid apart from a couple of holes for the idle valve) and tapped it to M6
and then made a P-clip to support the pipework. Its nice and solid now so no more flapping about
