occasional gutlessness 99 GT

Hello all, I have a problem with my 99 Mustang GT. I've had this car for a couple of years and it's done this since I've had it but it is now getting worse. the car has over 230K miles on it and it is no race car, it's just a nice convertible I use on nice days. Most of the time the car runs fine but it has been after being stopped at a light and going on green the car will have little to no power and I can't get up to highway speeds. I've been pulling over and shutting the key off and restarting and it would run fine again. There is no CEL on and no codes present. Up until a couple of weeks ago this was usually one time a day if at all, now it is happening several times a day and I was wondering if anyone else has encountered and fixed this problem? I plan to add a few engine to body grounds and then start digging deeper into checking individual sensors and connections but any help would be appreciated, thanks.

I do have Forscan and the torque app, when I've ran a scan no codes have came up and I mentioned to a buddy that I might have to have him drive while I watch what is happening on the real time data, not that I know what the values should be but see if anything is looks wrong from when it's running good as to when its running bad. Thanks for the input.

Well I took the car out for a drive today with my laptop running Forscan and while it was running good everything was looking to be normal, after a while it started running rough and I was able to notice the fuel pressure drops down when it is running bad. At the lowest pressure and running the worst with my foot to the floor it was reading 3.5 PSI. I would have to think this is the problem, most times the pressure has been hovering around 40 PSI, now I just have to figure out why the pressure drops so low at times.