The car runs fine when under light load or if you drive like grandpa, but as soon as the boost comes on (anywhere above zero) it hesitates and stumbles. The problem is worse when the car is cold but is still very noticable at operating temperature. The higher the boost level the worse the problem. The only code the car has is a code 44 o2 lean. The ses light only comes on if you drive on the highway for 30 min trips, it has never come on around the city. I do not want to confuse this with the tcc shudder. The problem occures at any speed 50 kph around town or 100kph on the highway. The following parts have been changed or swapped in the last few weeks none of them helped the problem:
sc rebuild along with coupler
sc base gasket
tb gasket along with a good cleaning
egr gasket and cleaning(also tried swapping one from another car)
lower intake manifold gasket
boost control solenoid
plugs, wires, fuel filter, air filter
o2 sensor
coils( tried swapping from another car)
ignition module( tried swapping from another car)
pcm(tried swapping from another car)
removed cat
Fuel pressure checked out at a perfect 45 psi

I am wondering if this could be a timing related problem. Which sensors control timing or are related to the timing system. My only idea is that the sensor (*) are advancing or retarding timing when they are not supposed to be. Any ideas would be greatly appreciated.

Sounds like a fuel pump problem to me. Anyone know how to test it without dropping the tank?

Mine would behave the same, except had the opposite reaction to heat.

fuel pressure checks out so I dont think it is fuel pump related. The fuel pressure is a steady 45 psi. When you rev the engine in park or in gear the pressure never drops below about 42 psi and peaks at about 50 psi.

Had much the same problem with my 97 Sonoma. Fuel pressure was testing ok but ended up attaching guage and checking it under actual driving conditions and found out the pressure was dropping once the engine was under load on the highway. Replaced the fuel pump & filter and problem went away. I later checked the filter and found that I could hardly even blow through it. I guess the pump could supply enough pressure at low volumes required for idle & light throttle but not once the engine required more fuel for extra load.

Flatlander ( In Humboldt, only 60 miles east of you)

Anyone with more suggestions ? Your help would be great !
Thanx in advance

starting fluid or some other way of adding fuel to the car aside from letting the car itself do it will tell you weather or not it is fuel related. Im not sure if its safe though, i posted about it earlier in general chat

If the O2 is new (and isn't a bosch), and you still have the lean code, with good fuel pressure, rule out all ignition problems right away. They'll show rich.

I'd be looking at fuel injectors if I were you. It'* rare, but your symptoms seem to point that way.