elo, i dnt know much about audis, but frm what you saying about lack of responsiveness and general low down power, have a lil look at the plugs, check the air fuel ratios all good?, skim the head, it does have relatively high mileage now, so maybe even do a dry compression test?, exhaust system and intake is a good start also, get a more free flowing setup in general, get that beast breathing beter and then look at the fueling.....? let me know how you get on, Rob.