When you put your right foot to the floor on a properly running MB turbo diesel it will be running with the wastegate open from about 2000 rpm or a little less all the way out to the limit (~5100 rpm). The wastegate holds the boost pressure below 1 bar. Eventually some wastegates WILL fail - most fail by not completely closing or by opening too soon tnus holding boost well below the ~0.9 bar limit. A few will stick shut and that will allow boost to build up to 2 bar (or more) and it only takes minutes at that boost to melt pistons or do other serious (and VERY expensive) damage - and there is usually NO warning. Just climbing a mile long hill flat out can do it! The overboost protection circuit guards agains that and it should be quite noticable when it kicks in. The engine isn't just limited in power as when the injection pump governor hold the engine to 5100 rpm - it drops instantly about 30% in power when the pressure signal to the ALDA is shut off and all pressure controlled fuel enrichment is turned off!

Running with the overboost disabled is fine as a test, but to do it for any length of time is NOT prudent although MOST turbos do not have the wastegate fail closed. If your turbo should fail that way with the overboost protection disabled, you could turn you engine into a doorstop/anchor VERY quickly.

Marshall