something is either A) sticking on your carberator, ie like the linkage at the carb or the cable itself is sticking in the tube.....B) something is hanging up on your cable, like the cable assembly is being pulled by something.....C) check your floor mat, make sure it isn't resting on the pedal assembly at all.
you can start by firing up the car, opening up the hood, and then either have someone press on the gas pedal or manually operate the linkage yourself and see what happends. if the linkage on the carb is binding up you will clearly see it, grab yourself some silcone spray and go to town.....if the cable is binding (probably won't see it, acts like linkage on the carb except you won't see the cable twisting in reverse).....again grab some silcone and go to down on the cable itself and the carb linkage.
oh and also check the connection at the gas pedal itself, that too could be binding.
i personally have never seen a carbed up bmw (except the lovely 2002's) but operation is all pretty much the same when it comes to this type of set up
sexually assault a member of the VW community? if you belong to dubdojo or swov.org they will gladly circle their wagons and support you.