James, yes it is definately worth checking with the actual serial number for the rev limiter and likewise just to make sure that there wasnt a requirement for the boost to come in late (seems very unlikely)

Then once that is ruled out, its just a case of finding out why the turbo is allowing gasses through the wastegate when it shouldnt, which will pretty much have to be either the actuator is weak, or a bent or chipped penny valve (like Stu mentioned)

The good news is that the turbo is obviously working fine once spooled, the map seems good, and the engine is obvioulsy working well once it sees boost too, so cant be a big deal to fix.


Si do the following:

Find a hill you can use for testing thats near by, put it at 2500rpm in 3rd and go full throttle, and observe when it first makes a bar of boost. so that you can check if any changes you make have worked without needing another trip to the rollers. As you can reproduce this test easily.

Send the chip serial number to stu just to rule out it being deliberately mapped like that

Check that the actuator has suffficient preload by disconnecting it and making sure that there is tension about 5mm or so before it lines up with the hole in the arm

If both the above are ok, take the downpipe off and inspect the penny valve (if you are in doubt I can have a look for you)