2004 Jeep Liberty losing power at 'low' altitudes while driving - acts like bad gas but isn't

I have a 2004 Jeep Liberty with over 130,000K. I live at 9K feet in elevation in the mountains of Colorado. While driving to Maryland last fall, my Jeep starting periodically (every couple of days; up to 2 times a day) going thru a ‘sluggish’ phase, typically around 40miles per hour while excelerating, that it loses power & sort of acts like it has bad gas (starts hesitating). I added several bottles of top of the line Fuel Injector Cleaner to the gas tank, as well as the directly into the carbuerator to clean out the system, and used high-octane fuel in numerous tanks while driving from Maryland to Texas. Nothing really made a difference. Had all 4 Oxygen Sensors changed. Problem continued driving thru Dallas, and check engine light came on once, but then went off before I arrived in Colorado Springs. The dealer in Colorado Springs said they were not able to determine problem without the light on. Since then, the jeep does fine at high altitude where I live, but continues to have sluggish problem around same exceleration speed of approx. 40mph at lower elevation only. Getting ready to make another long road trip, and concerned about lack of power when I might need it and/ or car trouble while on the road. Any ideas? Thank you.

I used to live near Steamboat Springs in Colorada, at about 6500 ft. Some cars, at least in the past, sold in Colorado come equipped with a “high altitude kit”. Maybe yours has this, and while it is good for 9000 feet, it is causing problems at the lower altitude. Do you know if your car has this high altitude kit?