Yes it is normal to lose some off the line power. Think about it.... you are idling at 7000ft at zero boost. The air density is less than say at sea level. It takes the turbo to spool up to provide you with boost. Just because you are turbocharged doesn't mean that you won't lose ANY power at altitude.

My 2001 Dodge-Cummins powered loses some power when I take it to Lake Tahoe, Calif. It is 6,000ft above sea level. I also notice my truck was doggier on take off, smokes more AND under wide open throttle, I couldn't build as much boost PSI as I could in Sacramento. I could see up to 36psi boost at sea level. At 6,000, I could only get about 29psi.

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My Truck.. 2007 DODGE, 5.9 Cummins, 6spd stick, 4X4. My car..1977 240D, OTHER WHEELS...1955 VW Oval window bug, European Delivery (Holland) with a 1700cc, 2 barrel, Porsche drum brakes. 1939 WILLYS Pick-up. 1967 Triumph 200cc Tiger Cub. 1976 Honda 550F 4cyl Motor Cycle.