hi! your problems sound very similar to what i had on my car,but it started to want feel as if it was going to stall at every junction i stopped at, it did stall once about 2 month ago, it was late about 11pm and cold about to pull out of junction the car stalled,the engine light came on. luckly it started first time and got home. called lexus dealer and they said no issue or problem, so looked on club lexus american site and some guys the have used this bg44k and were saying how good it was,locked on audi,ford and other forums were its been used and these problems issues that they had disapeared after use. on the offical bg44k website they say this product was produced with the help of audi in germany for there audi rs4 because of alot of carbon build up. i tried 1 can on my lexus and a can of bg244 for my dads bmw525d and what a difference it made, both engines are much smoother,responsive a no more as if about to stall.now after 2000 miles of use performance has not tailed off and mpg is about 3 mpg better than before use.ps started to use vpower instead of normal unleaded,less ethanol in vpower which is the cause of carbon build up,only down side is the stuff is £20 a can but only need to use every 10000miles.
hope this is of some help.
mike