How do you KNOW the GPR is good without testing it... I have seen brand new ones that come out junk.

Wish I was closer I would give you a hand...

Buy a STANCOR GPR and be done with it

I have been quite happy with my GPR109's from napa...$32.00 and I am done.

Now truck will start but will not stay running unless you give it fuel,but as before, if plugged in will start and stay running?

Its time to take it somewhere that has the equitment to data long and see whats going on.

Just did cylinder contribution test,computer stated cylinder 8 contribution fault or balance fault,code po284.any ideas/

#8 almost always fails... Its the Long lead injector...

I would check HPO pressure when cranking, Duty cycle when cranking, Check the fuel pressure, Buzz test it...

hpo psi is 1750 when cranking,buzz test done good,fuel psi unknown but wouldn`t there be other issues if fuel psi was low?also would #8 cylinder fault cause cold start problem?

#8 is nothing to worry about. 90% of the trucks on the road right now would fail a cont test with #8.

Check your ICP sensor and see if there is oil leaking into the plug area. Check your HPO res and make sure it is full apon first crank in the morning...

Just a thought but are there not two relays to change? One for the glow plugs and one for a air intake pre heater?
I know on the 2000 F350 I have we just went through the same thing, poor cold starting. There were two relays for pre heat so we just changed them both.
Starts great now.
Just my 2 cents.