signum 2.2 direct petrol power loss

[canon1982]

Hi there new to the site bought a signum 2005 2.2 direct nothing but problems 

The car broke down would not rev up and was in limp mode aa came out and blanked of egr valve that seem to help but not much 

the car will rev upto 5000 rpm then start miss firing turn on off to stop miss fire and also drives like a 1ltr

Took car into vauxhall and they said compression good fuel pressure good but lots of fault now the whole time this was there the egr valve he kept blanked off  codes which were 

p0400-62 egr valve malfunction

p1405-06 egr circuit low voltage

p1403-08 egr circuit malfunction

p0105-06 manifold absolute pressure sensor circuit open - low voltage 

p1112-03 swirl actuator malfunction

p0100-06air mass flow circuit low input

p0110-14 intake air tempsensor circuit high input

p0191 - 02 fuel pressure actuator voltage

And when you rev passed 5000rpm it comes up with miss fire codes but they go when you turn car on and off 

The car has had new fuel filter full service and secound hand maf sensor from scrap yard 

vauxhall have come back to me and said that the wiring harness is not in the best condition but ok so to get a real diagnostics to have new one fitted at £800 

the car does drive whilst egr valve blocked off but not like a 2.2 more like 1.2 but as soon as you rev passed 5000 rpm all lights come on 

also when you un blank egr valve car does not drive at all 

what im trying to ask to anyone that can help could bad egr valve or map sensor cause this or do we believe the harness needs replacing or do i scrap the car lol sorry this is so long and hope this is on the right topic many thanks stuart