Misfiring badly, then cut out now won't start?

[jimbotd5]

After some help please, I've got a 172 2002 and it yesterday it started misfiring and popping like it was running out of fuel. Eventually died and would not start. Put it on a code reader but no faults stored. I narrowed it down to what I thought was fuel pump so parked it up and went and got a pump today (and another gallon of fuel to be on the safe side) and it started first time but misfiring when revved. It then started to rev quite clean so I gave it one big Rev and as it peaked it just lost all power and died like as if it sucked all the fuel out of rail and there wasn't any to replace it, now it won't start again so I changed the pump with another one and it's the same fault now just wings over but won't fire! Fuel is getting to rail. Could it be faulty injectors/rail? If it's left overnight it'll start again but not for long suggesting fuel running back/not enough pressure? I'm losing it slowly with this car now only had it a month and it's worked for two full days without faults so any help appreciated pleeeeease!