Basically I've had endless problems with my Vl since converting it to manual its been breaking down at around 3,000 rpm and the tachometers having Spazims on its own. Also drinking heaps of fuel. I've changed so far Coil Leads Plugs Fuel filter and both pumps Computers Crank angle sensor Air flow meters

Sounds like you either have a poor connection on the CAS or the you are getting interference in the CAS wiring. Did you change wiring looms at all? Check that all earths are making clean contact. The CAS loom is a shielded cable - it has a metal braid surrounding all the cores and this MUST be earthed, otherwise the spark plug leads will induce a signal into the cas loom and the ecu will get false signals. I think it is earthed at the ecu end of the loom.