as you might of read i changed the primmer pump on my 99 cummins, due to low pressure , now after driveing home from work i let it idel for a a short while and it beguun to miss not terrible but it was there , rev it a bit and it went away, let it idel and it would come back, it is not a continuoes miss , so im asking what could it be injector or pump , fuel pressure at 10 psi, if you rev it hard it drops to 4 psi, any help would be great, thanks,