When I step on the gas pedal to fast my "90 300 CE has a long delay before it takes off. If I fether the pedal lightly, it speeds up slowly and then will maintain the spped fine. I've recently done a tuneup including new fuel filter. My parts guy thought it might be sensor on the back of the fuel injection "distribution box", but when he looked at it today, he said it wasn't leaking (as he had seen before) and didn't want me to just buy one because they are expensive. Any ideas?