Need Opinions Asap Rb25det Issues

[Cupcake]

so i have a ser 2 rb25det cefiro, kkr480, greddy plenum stock injectors and ecu (have 550's and haltech waiting)

Never missed a beat, i built this car.

Car was purchased as rolling shell with 'big fuel pump' unsighted so i have no idea what it is.

drive for 2 hours today. go to shops, wait 1 hour, drive car get 200m sounds like its running on 5 cylinders.

pull over 4 hours later in the rain ive checked spark, fuel, compression. plugs, blow by, crankcase pressure, afm..... no idea

then came good but still sometimes missfiring bad. drive 1 hour back home get 2 streets away and car just starts to die in the ass.

BUT in recent when under load this loud whistling straining noise has been coming from the fuel pump....

can this pump be dieing? cos the missfire was intermitten, sometimes dropping a cyl and then running fine, try and bring it under load (boost) it would just cough and splutter.

Bearing in mind this car has sat and im about to change the 'unkown big pump' to a brand new bosch 040 ive had sitting here and replace the new fuel filter i put in when i put the motor in..

Is this my issue? or are my splitfires f**ked? any ideas?

[Hibino]

If you've already got the pump you aren't losing anything by swapping it over. If you know the 040 is good and it fixes the problem then it's all good.

[Cupcake]

yesh the 040 is brand new. in box.

But is this my issues, yes it is problem solving but has anyone had this problem so im not chasing my tail.