2006 Sprinter in limp mode?
 

i have a 2006 sprinter. it goes into limp mode fairly quickly. wont rev above 2300 rpm and no faster then 60mph on flat. no mil code light on the dash until yesterday.

P0234 turbo/super charger overboost condition.

would a broken turbo resonator cause this code?

The cat converter most likely needs replacing. The engine is not getting the exhaust out and it's producing overpressure in the engine. Don't drive it for long like this your turbocharger won't survive it. This can also be caused by a clogged airfilter.

^x2

Check all the hoses going to the intercooler. Little tears in those cause some interesting issues like full boost till about 45 mph then no turbo at all until a restart..