Check the fittings at the warm up acccumulator, at the front of the intake manifold (2 fuel lines going to it). Mine had similar symptoms and one of the fittings had an orifice in it which was clogged (dirty). I removed the orifice and it ran fine. I ordered a new fitting from the dealer and it didn't have an orifice in it (?). Car runs great now so I don't worry about it

EDIT: I just noticed the date of this post; oh well, maybe it'll help someone

__________________
1983 380SL
1995 C280
1995 S500 coupe
1990 Mazda Miata
2004 Suzuki Hayabusa