17-11-2014, 08:47 PM
I may be wrong, but I would have thought that a restrictive exhaust would help hold boost as it couldn't empty the bores quickly enough.
The wastegate may be the problem, possibly a slightly weak spring, or the wastegate valve/flap burnt away/not seating properly.
I would check you induction side as well in case there is a restriction. Under initial load, the turbo may be able to cope with the air demand. Under continuous/prolonged load, a restriction on the inlet side pre turbo would starve the turbo of incoming air supply.
The wastegate may be the problem, possibly a slightly weak spring, or the wastegate valve/flap burnt away/not seating properly.
I would check you induction side as well in case there is a restriction. Under initial load, the turbo may be able to cope with the air demand. Under continuous/prolonged load, a restriction on the inlet side pre turbo would starve the turbo of incoming air supply.