Found the
problem .. it's not the turbo! After unbolting the DP and pulling it back, the turbine looks fine, so I went down to under the radiator to drain the coolant out the system and saw that a silicone hose has burst and an alloy pipe is damaged, between the IC outlet and the MAP sensor. Looks like the clamp has squished the alloy pipe, allowing pressure to escape, eventually blowing off and damaging the hose in the process.
This hose has blown off before, so I want to sort this out for good, so I want a one-piece, strong pipe made up with good beads on the ends and a fitting for the water injection nozzle, maybe made out of stainless steel for strength.
Might just carry on and remove the turbo and send it off to CR or Owens for a health check and maybe an upgrade!
CR Turbos quoted me £200 to upgrade it to a 2871R, £300 with a motorsport metal bearing cage for strength.