Sounds like it's going into limp mode ? Strange that the EML hasn't come on though. Does the management light come on when you turn the ignition on for the bulb check ( not cranking the engine, just switching on ) ?

In some instances the ECU doesn't log a fault if the parameters of the various sensor readings are not outside the norm, but are enough to cause confusion to the ECU as it's not an expected response for the given conditions the other sensors are reporting.

A favourite cause of limp mode without EML is an over boost condition of the turbo as the variable nozzle mechanism can stick / gum up by carbon deposits. This happened on my Seat Leon 1.9 TDI once and the only way I could read the error memory was with VAG COM software. The best advice would be to get the car into a good VAG independent garage and get any codes read out first and take it from there.