Checked for vacuum build up in tank first.....cap came off without a 'big suck' and still ran poorly with cap off......so probably not the problem.......I had this in my boat a few years back (OMC Sterndrive) and it took the 'Marine Mechanics' quite a long time to find it and do a simple fix

Changed fuel filter..........unfortunately also no help.........thickish 'caramel milk' from input side of filter....so needed changing even though < 100miles

That leaves 240DieselDog's suggestion of the fuel strainer............with last drive noted tends to cut out on corners........making me think of the gunk in the bottom of the tank slopping around on corners and building up on the screen.......clearing after stopping for a while would also be easily explainable

My first job when trying to get this car going was to empty the tank........by undoing the connection to the pump and flushed it through with a few extra gallons.......I understand gunk could remain in the bottom of the tank and the strainer would not be cleaned doing this.........but removing the tank looked like a big job

Have looked at the fuel line from the tank to the pump........noted the much larger nut which I presume holds the strainer

I would appreciate some advice on undoing these connections to the tank.....the big nut looks like a challenge........can the strainer be removed this way for cleaning?