as above my cars showing fault code 21 and seems to be running alot slower than it should be, i previously thought it was a boost issue but then my friend said its in limp mode, is this true? would coolant temp sensor cause the car to be in limp mode?

any help much apreciated

 

how boost is it making? If the car isn't fully warmed up then its possible it won't be allowing full boost to be made. The car doesn't know if it's warmed up if the coolant temp sensor is busted (code 21 = coolant sensor)