XC70 Hesitating while accelerating at high speeds

[cmf0707]

I am really trying to love my "new to me" Volvo, but it has been less than loving to me back. I purchased this 02 xc-70 in January with 138,000 miles on it, after a serious car accident that left be badly banged up. I chose Volvo because of safety and reliability. Since the car has come in to my hands I have had to replace a front left tie rod, a blower motor, the gear shifter, brake line, tires, drive shaft (misdiagnosed, was actually..), front right CV joint, AND left rear spring. I knew this car had some issues before purchasing but did think that it would be anything close to this magnitude.

2 days ago I picked the car up from the latest repair drove it Vail, Colorado and while driving on I-70 the car started to hesitate while accelerating uphill at high speeds (60-75mph). It had never done this before. I was driving at extremely high altitude (10,000-12,000 ft).

Is it:
the spark plugs?
the fuel injection system?
drity fuel filter?
air filter?

PLEASE PLEASE help, I'm about ready to donate this car to a mechanic with extra time.

[jda2000]

any check engine lights?

if you are asking if it is a dirty fuel filter, air filter or spark plugs, then you are past due my friend.

Replace those items ASAP if you don't know the service history of the car.