Check your real speed with a GPS, you will find out that you are not going at 55 mph.....I cruse my A3 on I-75 with the cat from Syrose @ 55MPH. the tack says 2200rpm and it goes just fine. Remember the cat is not a chevy big block.
And the other poster....going 60 mph with a loaded A3?.....they must be some A3's with a modified tranny or too much sun in the head.