olly986

hi boxsterian
it is funny but you seem to have similar problems with your 97 as I had with mine(i have since change for an 2000 S)
the airflow unit is very expensive I kept the old one as a souvenir on my office shelf, it is only made by bosch and to my knowledge cannot be purchase outside an official porsche part supplier, I even tried Germany but the cost in Euro is around €500.
this unit as it is called regulate the air flow going into your engine and when faulty your motor will not run on 6 cylinder but less and causes misfire.
an other problem that I encounter is with the water pump which litterally snap, maybe you should keep an eye on this too, it snapped the supply belt and everything on the boxster in run by this belt (this is NOT the timing belt as there isn't one on the Box but a chain is used instead)
If you manage to buy and change the airflow mass unit yourself you will have to get it set up with a porsche approved electronic unit which connect under the passenger side of the dashboard.
I hope you can get your car sorted out quickly and cheaply to get you back motoring
it is madness to deal with a porsche dealership to repair a 97 Box, find a good local porsche specialist which will charge probably half the cost and have all the needed tools.