fuel sensor

I'm trying to fit my new tuning box to my car. I can't remove the fuel sensor clip. I've flicked the grey clip so it's out and tried pulling it out with pliers. I can move it from side to side, but can't remove it. Any help to remove this with be much appreciated

Hi all I'm new to the site and have joined in the hope someone can help me. I own a C220 sport from1994 (W202) with automatic 4 speed box. Issue :- sometimes, completely random times, the car will when slowing down to a stop or even just slowing down, she stalls. Will start straight away...