I can't quantify the pressure drop. I had some issues with it running really lean a couple of years ago and the techo with the dyno machine had a pressure guage on the fuel line and he showed it to me and you could visibly see the pressure dropping as we spoke. He suggested that this was why it would be hard to start. My gut feeling is given enough time it drops to almost nothing. Interestingly if I leave it for a couple days it starts straight away (like it should in my opinion). Although I have only run one tank since I replaced the fuel pump (a bosch unit) fuel economy has jumped from a long term average of about 12.5l/100km to about 15l/100km (not good for my wallet). I t drives ok once it's running. No I haven't had it check for fault codes should I take it to Toyota.