a6 feels sluggish
 

Hello
i bought a 99 audi a6 2.8 quattro.but the engine feels very sluggish.i can never get the sudden pickup from 0.i changed the air filter,changed plugs too.put a fuel injector cleaner as well but i see no difference.it improved a bit after putting the new air filter in coz the old one was clogged.but i never get that quick acceleration.
please help

thank you
kushan