Very usefull thread guys thanks.
I have P0422 coming on so I'll start with new vacuum lines first.

 

I have had this code come up now .... just the next in a long ine . As far as I can tell I think the pump is at the front of the car by the horns and fog light underneath the air filter box om my 00 2.8.. I think I saw it when i had the front end off for my timing belt.
I don't understand why vacuum leaks would cause this .. I would imagine I have to check the pump itself and all the piping from the pump up to the combi valves ... I guess the real question is how is this measured ..

update.. so i broke out my ETKA .. and not being one to always ask for help without research i came up with a bit of a theory ..

it looks like the SAI pump pumps the air through some big pipes and to the combi valves one on each head .. these combi valves kind of look like some kind of diaphragm device . I think maybe the vacuum pulls op on the diaphragm opening a pathway for the air to enter the heads ?

Is this why a vacuum leak can cause this ? because the combi valve are not opening ?

I get the error every couple of weeks after reseting and they always come on together .. i would assume it has to be something common such as my pump crapping out or a vacuum leak to the combi valves so neither one opens fully .. anyone care to conmment ?

..further update .. the oxygen sensor apparently triggers this error .. so given both oxygen sensors for these codes are completely independant i am suspecting the SAI pump itself or the vacuum supply to the combi valves ..logic says it's cheaper to replace vacuum lines ...