I got a series 2 the other day and it runs well and sounds smooth but once its warmed up it just doesn't want to rev up at all. Could this be due to a warm up regulator or similar?

 

Most likely a fuelling issue, check co first, and change the fuel filter anyway.
tabetha

 

could be the wastegate. my missus rs once warm would stop reving and it turned out to b the wastegate sticking i put a stronger actuator on and it fixed the prob but i still need to change the wastegate as i know the prob will return